1. Mr. Smith has absolutely no _______ (同情)for students who get caught cheating in exams.
2. “Can I help you? ”a voice came from behind the _______ (柜台)when he entered the store.
3. When they heard the _______ (警报)they even did not realize what had happened.
4. The headmaster is to _______ (陪伴)a group of American students on a tour of our city.
