You are presented with the quiz "What is part of an animal's excretory system?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "organs of excretion make up the excretory system" and "leptospiral organisms cause infection in the kidneys and are excreted in urine". 

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


 

      kidneys     