You are presented with the quiz "what have a circulatory system with one or two hearts that pump blood" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "mollusks have a circulatory system with one or two hearts that pump blood" and "clams are mollusks that live in the sea or in freshwater". 

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


 

     clams      