Explanation:
Vapour pressure is the pressure exerted by the vapours of a liquid in equilibrium with its solid or liquid state. The vapour pressure of a liquid depends on various factors such as temperature, intermolecular forces, surface area, and volume of the liquid and vapour phase.

Effect of temperature on vapour pressure:
The vapour pressure of a liquid is directly proportional to the temperature of the liquid. As the temperature of the liquid increases, the kinetic energy of the molecules increases, and more molecules escape from the liquid surface to form vapours. Thus, increasing the temperature of the liquid increases its vapour pressure.

Effect of surface area on vapour pressure:
The vapour pressure of a liquid is also affected by the surface area of the liquid. A larger surface area provides more surface for the molecules to escape and form vapours. Thus, increasing the surface area of the liquid increases its vapour pressure.

Effect of volume of the liquid phase on vapour pressure:
The volume of the liquid phase does not affect the vapour pressure of a liquid. However, if the volume of the liquid is reduced, the concentration of the liquid increases, which increases the intermolecular forces between the molecules. This, in turn, reduces the vapour pressure of the liquid.

Effect of volume of the vapour phase on vapour pressure:
The volume of the vapour phase also affects the vapour pressure of a liquid. If the volume of the vapour phase is increased, the concentration of the vapour decreases, which reduces the number of molecules escaping from the liquid surface to form vapours. This, in turn, reduces the vapour pressure of the liquid.

Effect of decreasing temperature on vapour pressure:
As mentioned earlier, the vapour pressure of a liquid is directly proportional to the temperature of the liquid. If the temperature of the liquid is decreased, the kinetic energy of the molecules decreases, which reduces the number of molecules escaping from the liquid surface to form vapours. This, in turn, reduces the vapour pressure of the liquid.

Thus, the correct option is D, i.e., the vapour pressure of a given liquid decreases if the temperature is decreased.