B. elements and compounds
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Hello!</h2>
The answer is: Charle's Law.
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Why?</h2>
The law that states that the volume and absolute temperature of a fixed quantity of gas (ideal gas) are proportional under constant pressure is the Charle's Law, also known as the law of volumes.
The law describes how a gas kept under constant pressure tends to expand when the temperature increases and it's described by the following equation:

Where,

Also, to describe the relationship between two differents volumes at different temperatures, we have:

Where,

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In order of relative atomic mass.
Answer:
Option 2 and 4 are correct
Explanation:
The reactants in the attached image have more enthalpy and hence less stability as they are more reactive. Thus, Product is more stable than the reactants.
This is an addition reaction in which two reactants add up to form the product.
Very less activation energy is required as the reactants themselves are unstable, possess high energy and hence are very reactive.
Reactants have more energy than the products.