2. The only relative who looks after Tom is his

The text mentions 'Aunt Polly' multiple times in relation to Tom's care and upbringing. For example, 'At night Tom goes to his house, and listens in as Aunt Polly, Mrs. Harper, Sid, and Mary talk about him and Joe; he takes great pleasure in hearing them praise him. When Aunt Polly goes to bed, Tom kisses her, and leaves.' This indicates Aunt Polly is his primary caregiver. The options are 'uncle', 'cousin', and 'mother's sister'. An aunt is a mother's sister. Therefore, the correct answer is 'mother's sister'.