The relationship between static friction and kinetic friction is as follows:

Static friction is the force that must be overcome to initiate motion between two surfaces that are in contact. It acts when there is no relative motion and is typically higher than kinetic friction, which comes into play once the surfaces start sliding past each other. The reason static friction is greater than kinetic friction is due to the interlocking nature of the surfaces at rest. When they are stationary, there may be greater adhesion and surface contact, making it harder to start the movement.

Once movement begins, the surfaces may slide over each other more easily, reducing the frictional force, which is why kinetic friction is usually less than static friction. This difference in frictional forces is a fundamental concept in physics and engineering, influencing the design of various mechanical systems, safety factors, and materials used in applications such as brakes and tires.

The option stating that static friction is always greater than kinetic friction aligns with this understanding of how these two types of friction operate in practice, making it the correct choice.