What accounts for an increase in the temperature of a gas that is kept at constant volume ?

The correct answer to the question is : By increasing the pressure.

EXPLANATION:

Before answering this question, first we have to understand Gay lussac's law.

As per Gay lussac's law, the pressure of a gas increases or decreases by 1/273 th of its pressure at zero degree celsius; for every 1 degree celsius rise or fall of temperature at constant volume

In a simple way, the pressure is directly proportional to absolute temperature.

Mathematically P ∝ T.       [ P = pressure and T = temperature]

Hence, increase in pressure at constant volume may increase its temperature.

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