To solve this question, the user needs to know the definition of the terms "revolve" and "rotate" and their usage in the context of astronomy.

The correct answer is:

The Answer is: A

Option A, "revolves," is the correct answer. The sentence is describing the Earth's daily motion around its own axis, which is known as rotation. The verb that describes the Earth's rotation is "revolves." Therefore, option A is the correct choice.

Option B, "revolve," is incorrect. The verb "revolve" describes a celestial body's movement around another body in space. For example, the Earth revolves around the Sun. In this sentence, the Earth's motion around its own axis is being described, not its motion around another body. Therefore, option B is incorrect.

Option C, "None of the above," is incorrect. Option A is the correct answer, and option B is an incorrect answer. Therefore, option C cannot be the correct choice.

Option D, "Both a and b," is incorrect. While option A is the correct answer, option B is not a correct answer. Therefore, option D cannot be the correct choice.