You are presented with the quiz "an aquatic animal requires not having too much what in water?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "an aquatic animal requires great amounts of water to survive" and "too much algae can deplete the water of oxygen, making it impossible for aquatic animals to survive". 

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


 

     algae      