Final answer:
The correct relationship between the coefficients of kinetic and static friction is that the coefficient of kinetic friction is less than the coefficient of static friction.
Step-by-step explanation:
The relationship that is always true between the coefficients of static friction (μs) and kinetic friction (μk) is A. μk < μs. The coefficient of static friction is usually higher because it takes more force to start an object moving from rest than it does to keep it moving once it is already in motion. This means that the force of static friction, which opposes the initiation of motion, is typically greater than the force of kinetic friction, which opposes the continuation of motion.
The correct answer is D. none of the above. The relationship between the coefficients of static friction (μs) and kinetic friction (μk) depends on the specific materials involved in the frictional interaction. There is no universally true relationship between μs and μk for all situations. The values of μs and μk can vary depending on factors such as the roughness of the surfaces and the presence of lubricants. Therefore, none of the given options is always true.