Given the question: Question: Milo was rowing across a lake one day. He learned that his oar heated up a considerable amount when rowing through choppy water, but not so much when rowing through calm water. This made him realize that his oar moved slower through the (A) choppy water or (B) calm water  Do not use A and B to answer the question but instead, choose between "choppy water" and  "calm water".
The answer is:
choppy water