How many milligrams of HCl are contained in a 250. mL sample of a solution of hydrochloric acid with pH = 3.15?
a. 6.46 mg
b. 25.8 mg
c. 103 mg
d. 2.83 mg
e. 0.177 mg

The chemical released by activated cytotoxic T-cells to fight a viral infection is called perforin. Perforin plays a crucial role in the immune response by forming pores in the target cell's membrane, allowing other molecules like granzymes to enter and induce cell death, effectively eliminating the infected cells.

The chemical released by activated cytotoxic T-cells to fight a viral infection is called perforin. It is a protein that forms pores in the viral-infected cell's membrane, leading to its destruction. Additionally, activated cytotoxic T-cells release granzymes, which enter the viral-infected cell through the pores created by perforin and trigger programmed cell death (apoptosis). This process helps to limit the spread of the virus and promote the elimination of infected cells from the body.
The chemical released by activated cytotoxic T-cells to fight a viral infection is called perforin. Perforin plays a crucial role in the immune response by forming pores in the target cell's membrane, allowing other molecules like granzymes to enter and induce cell death, effectively eliminating the infected cells.

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Performing a pirouette standing up without faltering requires practice, balance, and technique. Here are some steps to help you improve your pirouette technique:

Proper Alignment: Start by standing tall with a good posture. Align your body by stacking your head, shoulders, hips, and feet in a straight line.

Spotting: Choose a spot in front of you and fix your gaze on it throughout the pirouette. Spotting helps maintain balance and prevents dizziness.

Preparation: Start in a relevant ballet position, such as the fourth or fifth position. Make sure your supporting leg is strong and stable.

Plie: Begin with a plie, which is a bending of the knees. This will help generate energy for the turn and provide a solid base.

Arm Placement: Position your arms in a way that supports your balance. In ballet, common arm positions for pirouettes include rounded arms in front of your body or extended to the side.

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The combination that will produce a precipitate is C) AgNO₃ (aq) and Ca(C₂H₃O₂)₂ (aq). When these two solutions are mixed, the ions Ag⁺ and C₂H₃O₂⁻ will combine to form a solid silver acetate (AgC₂H₃O₂), which will precipitate out of the solution. The other options do not involve combinations that will produce a precipitate.

The combination that will produce a precipitate is:
C) AgNO₃ (aq) and Ca(C₂H₃O₂)₂ (aq)

Let us discuss this in detail.

1. Write the balanced chemical equation for the reaction between AgNO₃ and Ca(C₂H₃O₂)₂:
  2 AgNO₃ (aq) + Ca(C₂H₃O₂)₂ (aq) → 2 AgC₂H₃O₂ (s) + Ca(NO₃)₂ (aq)
2. According to the equation, a solid precipitate, AgC₂H₃O₂, is formed as a result of the combination of AgNO₃ (aq) and Ca(C₂H₃O₂)₂ (aq).

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The new pressure of the gas is approximately 0.037 atm.

We can use Boyle's Law, which states that the pressure and volume of a gas are inversely proportional when temperature is held constant. Mathematically, this can be expressed as P₁V₁ = P₂V₂, where P₁ and V₁ are the initial pressure and volume, and P₂ and V₂ are the final pressure and volume.

We can rearrange this equation to solve for P₂ as follows:

P₂ = (P₁V₁) / V₂

Substituting in the given values, we get:

P₂ = (0.64 atm x 4.01 L) / 69 L

Simplifying this expression gives:

P₂ = 0.037 atm

As a result, the gas's new pressure is 0.037 atm.

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The substance that would be least soluble in carbon tetrachloride (CCl₄) is B) H₂O, also known as water.

CCl₄ is a nonpolar solvent, which means it dissolves other nonpolar substances more readily than polar substances. This principle can be understood by the saying "like dissolves like." Among the given options, H₂O is a polar substance due to the presence of hydrogen bonding between its oxygen and hydrogen atoms. This difference in polarity results in poor solubility between water and CCl₄.

The other substances are either nonpolar (C₁₀H₂₂) or have lower polarity (NH₃, CH₃CH₂OH, NaCl) compared to water, making them more soluble in CCl₄. In particular, NH₃ and CH₃CH₂OH are polar but can still dissolve in CCl₄ to some extent. NaCl, an ionic compound, is less soluble than covalent compounds, but its solubility is still higher than water's.

In summary, (option B) H₂O is the least soluble substance in CCl₄ because of its strong polarity and the difference in polarity between the two compounds.

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The correct answer is (B) (NH₄)₂S.

The fact that it did not form precipitates with Cl⁻, Br⁻, I⁻, SO₄²⁻, CO₃²⁻, PO₄³⁻, OH⁻, or S₂⁻ suggests that the compound does not contain those ions. However, the production of the foul-smelling gas H₂S when the solution is acidified indicates the presence of sulfide ions (S₂⁻). The only compound that fits this description is (NH₄)₂S, which is highly water-soluble and produces H₂S gas when acidified.

Let us learn this in detail.

1. Rule out compounds that form precipitates with the given ions (Pb(NO₃)₂, AgNO₃).
2. Rule out compounds that do not produce H₂S when acidified (KBr, Li₂CO₃).
3. The remaining compound, (NH₄)₂S, is highly water-soluble and produces H₂S when acidified, meeting all the criteria.

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The standard state of a solid or liquid is the state in which it is most stable at a standard pressure and temperature.

To be considered in its standard state, a solid or liquid must meet a few criteria. Firstly, the substance must be pure, meaning that it is not mixed with any other substances. Additionally, the substance must be at its normal boiling or melting point under standard pressure conditions.
Furthermore, the substance must be in its most stable state, meaning that it is not undergoing any chemical reactions or changes. This ensures that the substance is in its most energetically favorable state, which is necessary for defining its standard state.
Overall, a substance must be pure, at its normal boiling or melting point, and in its most stable state to be considered in its standard state. These criteria are important for accurately defining and comparing the physical properties and behaviors of different substances.

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The pH of a 0.050 M solution of hydroxylamine (NH_{2}OH) is approximately 9.48.

To calculate the pH of a 0.050 M solution of hydroxylamine (NH_{2}OH), we can follow these steps using the given Kb value (6.6 * 10⁻⁹):
1. Write the equation for the ionization of hydroxylamine in water:
NH_{2}OH + H_{2}O ⇌ NH_{3}OH^{+} + OH^{-}
2. Set up an equilibrium expression using the Kb value:
Kb = \frac{[NH_{3}OH^{+}][OH^{-}] }{ [NH_{2}OH]}
3. Assume that the change in concentration for NH_{2}OH is -x, while for NH3OH+ and OH- is +x. Thus, at equilibrium, we have:
[NH_{2}OH] = 0.050 - x
[NH3OH^{+}] = x
[OH^{-}] = x
4. Substitute these equilibrium concentrations into the Kb expression:
6.6 * 10⁻⁹ = \frac{(x)(x) }{ (0.050 - x)}
5. As Kb is very small, we can assume x is very small compared to 0.050. Hence, we can approximate:
6.6 * 10⁻⁹ ≈ \frac{x^{2}}{ 0.050}
6. Solve for x:
x = √(6.6 * 10⁻⁹ * 0.050) ≈ 3.63 * 10⁻⁵
7. Since x represents the concentration of OH-, we can now calculate the pOH:
pOH = -log10(3.63 * 10⁻⁵) ≈ 4.44
8. Finally, find the pH using the relationship between pH and pOH:
pH = 14 - pOH = 14 - 4.44 ≈ 9.56
The closest answer to our calculated pH is option b. 9.48. Therefore, the pH of a 0.050 M solution of hydroxylamine (NH_{2}OH) is approximately 9.48.

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The correct molecular structure for XeF4 is tetrahedral.

The Xe atom is surrounded by four fluorine atoms, and the electron pair geometry is also tetrahedral. The molecular geometry, which takes into account the lone pairs of electrons, is also tetrahedral. This gives a symmetrical molecule with a bond angle of approximately 109.5°.
                                   You asked for the correct molecular structure for XeF4. The correct molecular structure for XeF4 is square planar. However, since this option is not listed among the provided choices, the answer would be "none of these."

                                      The Xe atom is surrounded by four fluorine atoms, and the electron pair geometry is also tetrahedral. The molecular geometry, which takes into account the lone pairs of electrons, is also tetrahedral.

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The -log of the [H⁺] and the -log of the Ka are equal due to the relationship between them in the equation for the dissociation of a weak acid.

The statement "the -log of the [H⁺] and the -log of the Ka are equal" refers to a specific condition in which the negative logarithm of the hydrogen ion concentration (-log[H⁺]) is equal to the negative logarithm of the acid dissociation constant (-logKa). This condition typically occurs when the solution is at its half-equivalence point during titration.

The Ka is the acid dissociation constant and is equal to the product of the concentrations of the products of the dissociation divided by the concentration of the acid. The [H⁺] concentration is one of the products of the dissociation and is equal to the square root of the Ka times the initial concentration of the acid. Taking the negative log of both sides of this equation results in the -log of the [H⁺] being equal to the -log of the Ka. Therefore, this relationship allows for the determination of one value if the other is known.

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If [tex]HA^{0}[/tex] for a particular reaction is positive, it indicates that the reaction is endothermic, meaning that heat energy is absorbed from the surroundings. This leads to a net increase in the enthalpy of the system.

This can also be understood in terms of bond strength - if the bonds formed in the product(s) were weaker than the bonds broken in the starting material, energy would be released, and [tex]HA^{0}[/tex] would be negative. However, since the bonds formed in the product(s) are stronger than the bonds broken in the starting material, more energy is required to break these bonds and form the new product(s). Therefore, statements a) and b) are correct, while c) and d) are incorrect in this context.

In other words, if ΔH° for a particular reaction is positive, the correct statements that describe the reaction are: a) The reaction is endothermic. A positive ΔH° value indicates that the reaction absorbs energy from its surroundings, making it an endothermic reaction. b) There is a net increase in the enthalpy of the system. A positive ΔH° means that the enthalpy of the products is greater than the enthalpy of the reactants, resulting in a net increase in the system's enthalpy. c) More energy is needed to break bonds than is released by forming bonds. In a reaction with a positive ΔH°, the energy required to break the bonds in the reactants is higher than the energy released when new bonds are formed in the products. This leads to an overall energy absorption in the reaction.

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Answer:

Explanation:

The density of water = 1 g/mL

Mass of water = 159.0 mL x 1 g/mL = 159.0 g

q = m x c x ΔT

7.84 kJ = 159.0 g x 4.184 J/g°C x ΔT

ΔT = 7.84 x 10^3 J / (159.0 g x 4.184 J/g°C)

ΔT = 11.8°C

Therefore, the temperature change is 11.9°C.

Out of the given materials, the material that allows sound to travel 4 times faster than in water is copper.

Copper is an excellent conductor of sound due to its high density and low internal friction, which enables sound waves to propagate through it quickly and efficiently. In fact, copper is commonly used in audio cables and electrical wiring due to its excellent conductivity of both electricity and sound. Additionally, copper is also used in acoustic instruments such as trumpets and saxophones to enhance their sound quality and resonance. While steel, iron, and glass are also good conductors of sound, they are not as efficient as copper due to their higher internal friction.

Air and carbon dioxide, on the other hand, are poor conductors of sound and have much lower densities compared to solids, which hinders the propagation of sound waves. In summary, copper is the material that allows sound to travel 4 times faster than in water due to its high density and low internal friction, making it an excellent conductor of sound.

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This is an example of how the price per unit can vary depending on the quantity purchased. In this case, we can see that buying a larger quantity of the same vitamins results in a lower price per tablet.

To calculate the price per tablet for each bottle, we can divide the total price by the number of tablets. For the bottle containing 30 tablets, the price per tablet would be $8.99 / 30 = $0.30. For the bottle containing 100 tablets, the price per tablet would be $11.99 / 100 = $0.12.

As we can see, buying the larger bottle of vitamins results in a lower price per tablet. This can be a helpful consideration when deciding which size of product to purchase. It is also worth noting that this principle applies to many other products as well, not just vitamins. This situation is an example of "economies of scale" or "bulk pricing." In this case, purchasing the bottle with 100 tablets for $11.99 offers a better value per tablet than buying the smaller bottle with 30 tablets for $8.99.

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Answer: To calculate the empirical formula of the lead oxide, we need to determine the moles of lead and oxygen in the reactants and product, and then use these values to find the simplest whole-number ratio of lead to oxygen atoms in the compound.

Given:

Mass of lead (Pb) = 1.000 g

Mass of product = 1.154 g

First, we need to find the mass of oxygen that combined with the lead to form the product. We can do this by subtracting the mass of lead from the mass of the product:

Mass of oxygen = Mass of product - Mass of lead

Mass of oxygen = 1.154 g - 1.000 g

Mass of oxygen = 0.154 g

Next, we need to find the moles of lead and oxygen in the reaction:

Moles of lead = Mass of lead / Molar mass of lead

Moles of lead = 1.000 g / 207.2 g/mol

Moles of lead = 0.004830 mol

Moles of oxygen = Mass of oxygen / Molar mass of oxygen

Moles of oxygen = 0.154 g / 16.00 g/mol

Moles of oxygen = 0.009625 mol

Now, we need to find the simplest whole-number ratio of lead to oxygen atoms in the compound. We can do this by dividing the number of moles of each element by the smaller of the two values:

Lead: 0.004830 mol / 0.004830 mol = 1

Oxygen: 0.009625 mol / 0.004830 mol = 1.99

The ratio of lead to oxygen atoms is approximately 1:2, so the empirical formula of the lead oxide is PbO2.

Pattern 3 in a common mechanism involves the reaction of an electrophile and a nucleophile to form a new covalent bond.

An electrophile is an electron-deficient species that can accept a pair of electrons to form a new covalent bond, while a nucleophile is an electron-rich species that can donate a pair of electrons to form a new covalent bond. In this pattern, the electrophile and nucleophile come together and the electrons from the nucleophile attack the electrophile to form a new bond.

The reaction of an electrophile and a nucleophile is a common mechanism step in many organic reactions, including nucleophilic substitution and addition reactions. For example, in the reaction of a primary alkyl halide with a nucleophile, the electrophilic carbon atom of the alkyl halide is attacked by the nucleophile, leading to the formation of a new covalent bond between the carbon and the nucleophile. Similarly, in the addition of a nucleophile to an unsaturated carbon-carbon double bond, the electrophilic double bond is attacked by the nucleophile, leading to the formation of a new covalent bond between the carbon and the nucleophile.

Overall, the reaction of an electrophile and a nucleophile to form a new covalent bond is a fundamental mechanism step in many important organic reactions.

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An SN₂ reaction always results in an inversion of stereochemistry if the leaving group is bonded to a stereogenic center. This indicates that the nucleophile always attacks from the opposite side with respect to the leaving group.

Stereochemistry is the study of a molecule's three-dimensional structure. The only structural difference between cis and trans isomers, which are types of stereoisomers, is where the molecule's elements are located three-dimensionally. The chemical and physical properties of these stereoisomers may differ. Stereochemistry is a branch of chemistry concerned with "the study of the various spatial configurations of atoms in molecules." The systematic presentation of a specific area of science and technology
An SN₂ reaction always results in an inversion of stereochemistry if the leaving group is bonded to a stereogenic center. This indicates that the nucleophile always attacks from the opposite side with respect to the leaving group.

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An aqueous solution of Na₂SO₃ will produce a basic solution. Na₂SO₃ is the salt of a weak acid (sulfurous acid, H₂SO₃) and a strong base (sodium hydroxide, NaOH).

In water, the salt will dissociate into its respective ions:

Na₂SO₃ → 2Na⁺ + SO₃²⁻

The sodium ions will not react with water, but the sulfite ions will hydrolyze to produce hydroxide ions (OH⁻):

SO₃²⁻ + H₂O → HSO₃⁻ + OH⁻

HSO₃⁻ + H₂O → H₂SO₄ + OH⁻

Thus, the resulting solution will have a higher concentration of hydroxide ions than hydronium ions, making it basic. Therefore, the answer is (E) Na₂SO₃.

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Answer:

Explanation:

The mass-action ratio of the ATD-ADP system

Inspecting the area before a pesticide application is important to ensure safety, efficacy, and compliance with regulations.

Inspecting the area before a pesticide application is crucial for several reasons. Firstly, it ensures safety, both for the applicator and other people and animals that may be present in the area. By inspecting the area, the applicator can identify any potential hazards, such as water sources or sensitive vegetation, and take appropriate measures to avoid them.

Secondly, inspecting the area helps to ensure the efficacy of the pesticide application. By identifying the specific pests or weeds present and assessing the severity of the infestation, the applicator can choose the appropriate pesticide and application method to achieve the best results.

Lastly, inspecting the area is also important for compliance with regulations. Pesticide use is heavily regulated, and applicators must follow specific rules and guidelines to ensure the safety of the environment and the people and animals that live in it.

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The element with the greatest chemical activity among the options provided is a. aluminum.

Chemical activity refers to the reactivity of an element with other substances. Aluminum is more reactive than zinc, iron, and mercury due to its position in the periodic table. It belongs to Group 13 and has three electrons in its outer shell, making it more likely to form compounds by losing these electrons. This reactivity enables aluminum to readily react with oxygen, forming a protective oxide layer on its surface, which contributes to its corrosion resistance.

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The solubility of KNO3 is 155g/100g of water at 75°C and 38g/100g of water at 25°C. To determine the mass (g) of KNO3 that will crystallize out of the solution when 100g of its saturated solution at 75°C is cooled to 25°C, you need to compare the solubility at both temperatures.

At 75°C, 100g of saturated solution contains 155g of KNO3 per 100g of water. In a 100g saturated solution, the mass of water is not 100g, as it also includes the solute (KNO3). To find the mass of water in the solution, let's assume the mass of water is 'x' grams. The mass of KNO3 in the solution is (155/100) * x. The total mass of the solution, which is 100g, can be represented as x + (155/100) * x.  Now, when the solution is cooled to 25°C, the solubility of KNO3 decreases to 38g/100g of water. For the same 'x' grams of water, the amount of KNO3 that can dissolve at 25°C is (38/100) * x. The difference between the amounts of KNO3 at 75°C and 25°C is the mass that will crystallize out of the solution when cooled:  [(155/100) * x] - [(38/100) * x]
To find the value of 'x', use the total mass of the solution:
x + (155/100) * x = 100
Solve for 'x', and then calculate the mass of KNO3 that will crystallize out of the solution when cooled to 25°C.

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A solution is prepared by dissolving 14.0 g of NH₃ in 250.0 g of water. The density of the resulting solution is 0.974 g/mL. The mole fraction of NH₃ in the solution is 0.0560.

To calculate the mole fraction of NH₃, we need to first find the total mass of the solution. The mass of the solution is the sum of the mass of NH₃ and the mass of water:

mass of solution = mass of NH₃ + mass of water

mass of solution = 14.0 g + 250.0 g

mass of solution = 264.0 g

Next, we need to calculate the volume of the solution. We can use the density of the solution to find the volume:

density = mass/volume

volume = mass/density

volume = 264.0 g/0.974 g/mL

volume = 271.0 mL

Now we can calculate the mole fraction of NH₃:

moles of NH₃ = 14.0 g / 17.03 g/mol = 0.821 moles

moles of water = 250.0 g / 18.02 g/mol = 13.9 moles

total moles = 0.821 moles + 13.9 moles = 14.7 moles

mole fraction of NH₃ = 0.821 moles / 14.7 moles = 0.0560

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The uptake of molecules into the interior of another substance is referred to as "absorption".

The uptake of molecules into the interior of another substance is known as "absorption." This process involves the movement of molecules from a region of higher concentration to a region of lower concentration.

Absorption can occur through various mechanisms, such as diffusion, osmosis, and active transport, depending on the nature of the molecules and the medium in which they are dissolved.

For example, when a plant absorbs water and nutrients from the soil, the process involves the movement of molecules through the root system via osmosis and active transport.

Similarly, when a person takes medication, the drug molecules are absorbed into the bloodstream through the digestive system, where they can then travel to the target site and exert their therapeutic effects.

Absorption is an essential process in many biological and chemical systems, as it allows for the uptake of nutrients, the transport of molecules, and the delivery of therapeutic agents.

Understanding the mechanisms of absorption can help in the design of more efficient drug delivery systems, the optimization of agricultural practices, and the development of new technologies for environmental remediation.

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Answer:

The reaction quotient, Q, is the same as the equilibrium constant expression, but for partial pressures or concentrations of the reactants and products before the system reaches equilibrium.

The mass of a helium nucleus is slightly less than the sum of its parts due to binding energy.

In a helium nucleus, there are two protons and two neutrons. When these particles come together to form the nucleus, they release energy in the form of binding energy.

This energy release results in a mass deficit, which means the total mass of the helium nucleus is slightly less than the sum of the individual masses of its constituent particles.

Summary: The helium nucleus has a slightly lower mass than the sum of its parts because the binding energy released during nucleus formation leads to a mass deficit.

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a. hydrogen is right  option.Almost when the metals react with the acids at that time the liberation of hydrogen gas is happening and usually that is happening in the gaseous form.

Salt and hydrogen gas are created when an acid and a metal combine. This reaction's generic chemical equation is:

hydrogen gas + salt + acid + metal

For instance, the following reaction takes place when zinc metal and hydrochloric acid combine:

Zn(s) + 2 HCl(aq) ZnCl2(aq) + H2(g)

When acids  are reacting  with metals, they produce  the hydrogen gas. This is a consequence of the displacement reaction that is happening between the acid and the metal.

The acid losses up hydrogen ions (H+) which are  reacting  with the metal  in order to form  the hydrogen gas (H2). That adds up to the acidity and basicity of the solution.

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The correct trend in ionization energy is given by ordering III. The order is I < Br < Cl < F.

This trend is correct because ionization energy increases across a period in the periodic table from left to right, due to the increasing effective nuclear charge experienced by the outermost electrons. In this ordering, elements are arranged from left to right in the same period (period 5) with increasing ionization energy.

Ordering III gives a correct trend in ionization energy, as ionization energy generally increases as you move from left to right across a period on the periodic table. Therefore, F, being the element furthest to the right, has the highest ionization energy, while I, being the element furthest to the left, has the lowest ionization energy. The other orderings do not necessarily correspond with the trend in ionization energy.

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If the number of turns in a coil doubles, the magnetic field doubles as well(C).

The magnetic field generated by a coil is directly proportional to the number of turns in the coil. When the number of turns in a coil increases, the magnetic field becomes stronger.This is because each turn of the coil contributes to the magnetic field, and the more turns there are, the more they add up to produce a stronger field.

Therefore, if the number of turns in a coil doubles, the magnetic field also doubles. This is an important principle used in the design of electromagnets and inductors, where the strength of the magnetic field is a crucial factor. So C is correct option.

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