You are presented with the quiz "Unequal heating of the Earth's surface by the Sun causes ocean circulation and what?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "unequal heating of Earth 's surface by the Sun causes global wind patterns" and "finally, the pattern of tropical wind and ocean circulation is a key element of global circulation". 

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


 

     tropical wind      