Final answer:
Gas properties, specifically the volume and vapor pressure of water vapor, increase with an increase in temperature, demonstrating a direct relationship between these properties.
Step-by-step explanation:
The properties of water vapor, which is a gas, are affected by changes in temperature. According to the discoveries of early scientists, if you keep the amount of a gas and its pressure constant, then an increase in temperature will cause an increase in the gas's volume. This implies that temperature and volume are directly related. Moreover, vapor pressure of a liquid and hence related properties of a vapor will increase when the temperature increases, due to a greater fraction of molecules having sufficient energy to escape from the liquid.
Considering the above facts, the correct answer to the student's question about how gas properties change with temperature is that they increase with an increase in temperature (option C). The increase in kinetic energy with temperature causes gases to expand in volume when heated, as long as the pressure is held constant.