You are presented with the quiz "What does does the gravitational pull of the Moon on Earth's oceans cause?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "the gravitational pull of the Moon on Earth 's oceans causes the tides" and "high tide is the crest of the wave and low tide the trough". 

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


 

  waves         