The best explanation of verb mood from the options provided is:
- It is how a verb is used to express a thought.
Verb mood encompasses various ways that verbs can convey different attitudes toward the action or state expressed by the verb, including the indicative mood (stating facts), imperative mood (giving commands), and subjunctive mood (expressing wishes or hypotheticals). While options 2, 3, and 4 describe specific uses of verbs, option 1 captures the broader definition of verb mood in its role in expressing thoughts and attitudes.