The justification given by the student that the two opposite and equal forces cancel each other (and hence the truck does not move) is wrong. This is because the forces of action and reaction do not act on the same body (they act on two different bodies). So, there is no question of their cancellation. Actually, the massive truck does not move in this case because push (or force) applied to it is much smaller than the force of friction between the wheels of the truck and the road. Since the force of push is not able to overcome the force of friction, therefore, the truck does not move.