In this task, you are given two facts, and a multiple-choice question. Based on the given facts, answer the question with index of the correct option (e.g, "A").

Fact1: Antigens are molecules that the immune system recognizes as foreign to the body., Fact2: Antibodies are produced to fight antigens., Question: What happens when the immune system recognizes a foreign substance? (A) an area swollen with pus (B) The immune system fails (C) irradiation (D) Bacteria dies (E) Antibodies are formed (F) major threat to health (G) Something that causes allergies (H) Viruses reproduce
E