Final answer:
The vague pronoun in the sentence 'Chase visited Lewis after his swim meet' is 'his.' To make the meaning more clear, the sentence can be rewritten as 'Chase visited Lewis after Chase's swim meet.
Step-by-step explanation:
The vague pronoun in the sentence 'Chase visited Lewis after his swim meet' is 'his.' The pronoun 'his' is not clear because it does not specify whose swim meet is being referred to. To make the meaning more clear, the sentence can be rewritten as 'Chase visited Lewis after Chase's swim meet.'