You are presented with the question "What happens when the immune system recognizes a foreign substance?" and the following answer choices: 
- an area swollen with pus
 - The immune system fails
 - irradiation
 - Bacteria dies
 - Antibodies are formed
 - major threat to health
 - Something that causes allergies
 - Viruses reproduce

Now knowing that antigens are molecules that the immune system recognizes as foreign to the body and antibodies are produced to fight antigens, choose the best answer.


 

     Antibodies are formed    