Answer:
With three lines of defense
(your teacher may be looking for the answer white blood cells please read bellow just in case)
Step-by-step explanation:
It could also use to types of defense specific and non specific non specific being things like your skin specific being your white blood cells their are 3 lines of defense skin, then macrophages includes phagocytic white blood cells) and then the third includes B and T specif types of white blood cells