Respuesta :
Answer: Option (d) is the correct answer.
Explanation:
Net force is defined as the sum of total number of forces acting on a substance.
For example, when you and your friend are pushing a door in order to slide it open then it means that the net force is sum of force applied by you and force applied by your friend.
Therefore, the force applied earlier was less but it increase when your friend also started applying force.
Thus, we can conclude that if your friend stands behind you and helps you push, then the net force applied will increase.