In what way does a resisting force always act in relation to an applied force?

A resisting force always acts equal and opposite to an applied force, which aligns with Newton's Third Law of Motion. This principle states that for every action, there is an equal and opposite reaction. In practical terms, when a force is applied to an object, the resisting force works to oppose that motion with the same magnitude but in the opposite direction.

For example, if you push against a wall, the wall exerts an equal force back against you. This concept is fundamental in understanding how forces interact in various systems, such as in mechanics or structural engineering.

The other options do not accurately represent the relationship between resistive and applied forces. Perpendicular, parallel, and on a slant do not capture the essence of the opposing nature of these forces, which is fundamental to their interaction under Newton's laws.