Which explains verb mood?

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A. It is how a verb is used to make a command.
B. It is how a verb is used to ask a question.
C. It is how a verb is used to state a fact.
D. It is how a verb is used to express a thought.

D. It is how a verb is used to express a thought.

The correct answer is D. It is how a verb is used to express a thought.