Question

why is the top layer of the ocean the warmest?
a. the mixed zone contains saltwater.
b. salty water is less dense than pure water.
c. warm water is less dense than cold water.
d. warm water is denser than cold water.

Explanation:

The top - layer of the ocean is the warmest because warm water is less dense than cold water. Less - dense warm water rises to the surface. The presence of saltwater in the mixed zone (option A) doesn't explain why the top layer is warm. Salty water being less dense than pure water (option B) is not relevant to the temperature of the top - layer. Option D is incorrect as warm water is less dense, not denser, than cold water.

Answer:

C. Warm water is less dense than cold water.