Final answer:
A verb expresses actions (option a), states of being, or existence and is a crucial component of a sentence's structure. Verbs require a subject and can convey different times through tenses and show mood, like the indicative for facts, the imperative for commands, and the subjunctive for hypotheticals.
Step-by-step explanation:
Understanding Verbs
A verb is a fundamental part of speech that is essential in forming a sentence. Verbs primarily express actions, but they also convey states of being or existence. For instance, verbs like 'run' or 'speak' denote actions, whereas verbs like 'is' from the verb 'to be' indicate a state of existence. Verbs not only tell us what action is taking place but also when it is occurring, marking tenses like past, present, or future. Every verb requires a subject, which reveals who or what performs the action. Consider the sentence, 'The children are playing.' Here, 'the children' is the subject, and 'are playing' is the verb phrase. Moreover, verbs might change form to express different tenses or to agree with their subjects in terms of number and person – a concept known as subject-verb agreement.
Additionally, verbs can embody different moods to reflect how the action or state is viewed by the speaker. The indicative mood expresses facts or asks questions, the imperative gives commands, and the subjunctive deals with hypothetical or wishful situations. Verbs can appear in various forms, such as the participle form to act as adjectives or adverbs – for instance, 'The whistling man crossed the street.' Here, 'whistling' describes the man and is derived from the verb 'to whistle'.