情态动词表推测与义务 — 英语词汇题
题目
单句选择填空：1. He looks so pale that he ___ (must / can't) be ill; he should see a doctor at once. 2. You ___ (must / needn't) return the book to the library on time, or you will be fined. 3. The lights are on. Our teacher ___ (must / can't) still be working in the office.