What would cause a decrease in pressure of a gas?

A decrease in the pressure of a gas can occur due to both lowering the temperature and increasing the volume of the container, making the option encompassing both these factors the correct choice.

Lowering the temperature of a gas reduces the energy of the gas particles. According to the ideal gas law, as temperature decreases, the kinetic energy of the particles lowers, which in turn leads to a decrease in pressure if the volume is held constant. When the temperature drops, particles collide with the walls of the container less forcefully, contributing to a reduction in pressure.

Increasing the volume of the container also leads to a decrease in pressure. When the volume is increased, the gas particles have more space to move around. As they spread out over a larger volume, they collide with the walls of the container less frequently, which results in a reduction in the pressure exerted by the gas.

In contrast, increasing the number of gas particles would typically lead to an increase in pressure if the volume and temperature remained constant, since more particles would result in more frequent collisions with the container walls. Therefore, the answer that combines lowering temperature and increasing volume captures the conditions that lead to a decrease in pressure effectively.