Lesson 129 Seventy miles an hour1. Why is the policeman waving? 2. How fast must Gary have been driving? 3. Why didnt Gary see the speed limit? Pre-reading questions1. Why is the policeman waving? 2. How fast must Gary have been driving? 3. Why didnt Gary see the speed limit? Because he wants Gary to stop. He must have been driving at seventy miles an hour. He must have been dreaming.Grammar must + have been “那时一定是”； 表示对过去很肯定的猜测和推断： must have been (肯定) He must have been at home.Grammar must + ha
