It ... isn't? I think you may be mistaken (or your teacher has found some very obscure point to make).
If there is a problem that prompted you to think otherwise, can you give its context in the discussion section?
The resistance force that always opposes motion is friction. Friction is the force that acts between two surfaces in contact and it opposes the relative motion between the surfaces.
Friction always opposes the motion of a body by acting in the opposite direction to its motion.
The force on Earth that always opposes the motion of a body when it is in motion is called friction.
Friction is a force that always opposes the motion of an object. It occurs when two surfaces are in contact and resists the relative motion between them.
Friction is the force that always opposes motion. It occurs when two objects rub against each other, slowing down their movement.
Static friction is the type of friction that opposes the motion.
Friction
opposes motion
Friction, I think
friction
Friction always opposes the motion of objects by creating a force that acts in the opposite direction of the object's motion. This force resists the movement of the object, causing it to slow down or stop. Though friction can sometimes be reduced, it will always be present to some degree and affect the motion of objects.
Friction provides a retarding force. It always acts in the exact opposite direction of the motion of the object.