heating of the oceans by the Sun gravitational pull of the Moon earthquakes on the ocean floor changes in wind direction
I gave my students this multiple choice question: Which of the following is the major cause of tides?

Only one answer is correct among these 4 choices:
- heating of the oceans by the Sun
- gravitational pull of the Moon
- earthquakes on the ocean floor
- changes in wind direction

Could you tell me which one is correct?

gravitational pull of the Moon