Final answer:
The pressure of liquid varies with depth due to hydrostatic pressure, which is the pressure a fluid exerts due to gravity, increasing with depth according to the formula P = hpg. Option D is corrrect.
Step-by-step explanation:
The question you are asking relates to the concept of why the pressure of a liquid varies with depth. The correct answer to this question is D) Hydrostatic pressure. Hydrostatic pressure is the pressure exerted by a fluid at equilibrium due to the force of gravity.
It increases with depth because the pressure at a point in a static fluid depends solely on the height of the liquid column above it. This can be represented by the formula P = hpg, where P is the pressure, h represents the depth of the fluid, p is the fluid density, and g is the acceleration due to gravity. As the depth increases, the weight of the fluid above that point increases, thus increasing the pressure.
Archimedes' principle is related but distinct from hydrostatic pressure as it describes the buoyant force that arises when a body is placed in a fluid, causing an increase in pressure and resulting in an upward force on the body. Similarly, Pascal's law describes how a change in pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and to the walls of its container.