Final answer:
The correct sentence is 'He and they went swimming,' which uses the subjective case for pronouns in the subject of the sentence.
Step-by-step explanation:
The sentence written correctly is D. He and they went swimming. When constructing a sentence that involves pronouns as the subject, it is important to use the subjective case ('he,' 'she,' 'we,' 'they') rather than the objective case ('him,' 'her,' 'us,' 'them').
In English grammar, the subject of a sentence must be in the subjective case, which indicates that the pronoun is performing the action of the verb. In the sentence provided, 'He' is the correct form for the singular male subject, and 'they' is the correct form for the plural subject.
Therefore, the correct sentence features both pronouns in their subjective case forms, indicating that 'He' and 'they' are performing the action of going swimming.