You are presented with the quiz "What are molecules that the immune system recognizes as foreign to the body?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "antigens are molecules that the immune system recognizes as foreign to the body" and "an antigen is a molecule of carbohydrate or protein". 

So, what's the best answer to the question?


 

  Carbohydrates, or proteins.         