You are presented with the quiz "What does a pregnanct woman pass on to the fetus?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "passive immunity lasts only as long as the antibodies survive in body fluids" and "immunization in a pregnant woman produces both active and passive immunity in the fetus". 

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


 

   antibodies        