Which of the following is a rule for subject-verb agreement?

The selected answer is correct because it clearly defines a fundamental rule of subject-verb agreement in English grammar. When a subject is singular, it should be matched with a singular verb form to ensure grammatical accuracy in a sentence. For example, in the sentence "The dog barks," "dog" is a singular subject, and "barks" is the corresponding singular verb conjugation.

This alignment between singular subjects and singular verbs maintains clarity and coherence in communication. Using a singular subject with a plural verb or vice versa would create confusion and disrupt the expected grammatical structure, leading to sentences that sound incorrect or ambiguous. Thus, understanding this rule is essential for constructing grammatically correct sentences.