The correct answer is: C. decrease in viscosity of gas.
Viscosity is a measure of a fluid’s resistance to flow. It is caused by the friction between the molecules of the fluid. The higher the temperature, the faster the molecules move. This means that they have more energy and can overcome the friction between them more easily. As a result, the viscosity of a fluid decreases with increasing temperature.
In the case of a gas, the molecules are already moving very quickly at room temperature. When the temperature is increased, the molecules move even faster and have even more energy. This means that they can overcome the friction between them even more easily, and the viscosity of the gas decreases.
In the case of a liquid, the molecules are not moving as quickly at room temperature. When the temperature is increased, the molecules move faster and have more energy. However, they are still not moving as quickly as the molecules in a gas. As a result, the viscosity of a liquid decreases with increasing temperature, but not as much as the viscosity of a gas.