Read the sentences (1–3) and complete the rules (a–c) with the words in bold. (Đọc các câu (1–3) và hoàn thành các nguyên tắc (a – c) với các từ in đậm.) 1. A vacuum cleaner is a machine which/that we use to vacuum the carpets. 2. He’s the man whose sister eats organic food. 3. Sue is the girl who/that works at the local animal shelter. We use: a. _____________________ to refer to people. b. _____________________ to refer to things. c. _____________________ to refer to possession.