According to Newton's Third Law of motion, pairs of forces:
1. Must have the same magnitude.
2. Must point in opposite directions.
For example, if object A exerts a force on object B, object B will exert an equal force in the opposite direction on object A. This is commonly summarized by the phrase "For every action, there is an equal and opposite reaction."
Therefore, the correct statement from the options provided is that pairs of forces must have the same magnitude. This principle is fundamental in understanding the interactions between objects and how forces affect motion in the physical world.
