Answer:
B - the box pushing against the boy
Step-by-step explanation:
Newton's third law of motion also known as the law of action and reaction states that for every action there is equal and opposite reaction.
The action force is the force acting in one direction while the reaction force is the force acting in the opposite direction. for example, when a person wants to jump, the person exerts a downward force on the ground known as action force and also, the ground exerts upward force on the person known as reaction force.
If the action force is the boy pushing the box, what is the reaction force is the box pushing against the boy.