I think the answer is (B)...
For example, trees are dormant during Winter.
Answer:
It is a learned behavior.
Explanation:
Typically, tool use implies a complex behavior that requires training and observing someone else who already has that particular ability. Thus, this ability shall be learned by one generation from the previous one, which shows and teaches this behavior to the next one.
A) inform the white blood cells of the invader so it can be destroyed. This works because antigens are proteins, and proteins have unique complex structures; the combination of antigens on the surface of a pathogen will each cause an immune response in the body, and ultimately white blood cells are part the immune system responses to destroy this pathogen.