You are presented with the question "What are molecules that are recognized by the body as alien?" and the following answer choices: 
- parasites
 - Acids
 - heat or cold
 - negative
 - antigone
 - antibodies
 - antigens
 - blood cells

Now knowing that antigens are molecules that the immune system recognizes as foreign to the body and yes, foreigners are called Aliens, choose the best answer.


 

       antigens  