Pascal's Law explains how __________.

Pascal's Law, also known as Pascal's Principle, states that a change in pressure applied to an enclosed fluid is transmitted undiminished throughout the fluid in all directions. This principle is fundamental to understanding how hydraulic systems operate.

In the context of a hydraulic jack, when a small amount of force is applied to the smaller piston, it generates pressure throughout the hydraulic fluid. Because this pressure is transmitted equally, it can lift a much heavier load on a larger piston. Thus, a small jack can effectively raise a two-ton car because the force applied to the smaller piston creates a pressure that is sufficient to lift the weight on the larger piston. This illustrates the powerful mechanical advantage gained through the use of incompressible fluids in hydraulic systems, making the understanding of Pascal's Law pivotal for such applications.

Other options, while they may involve fluids in some way, do not accurately reflect the application of Pascal's Law.