Water at the bottom of the ocean contains more dissolved solids. Water at the surface of the ocean absorbs more energy from the Sun. Friction is created by fast moving currents at the surface of the ocean. Wave action transfers heat from the bottom of the ocean to the surface.
I gave my students this multiple choice question: Which of the following is the main reason water at the surface of the ocean is warmer than water at the bottom of the ocean?

Only one answer is correct among these 4 choices:
- Water at the bottom of the ocean contains more dissolved solids.
- Water at the surface of the ocean absorbs more energy from the Sun.
- Friction is created by fast moving currents at the surface of the ocean.
- Wave action transfers heat from the bottom of the ocean to the surface.

Could you tell me which one is correct?

Water at the surface of the ocean absorbs more energy from the Sun.