. Complete the sentences with must or mustn't.(Hoàn thành câu với must hoặc mustnt) 1. You help your mother with the heavy box. 2. Its very cold. You go out. 3. You wash your face in the morning. 4. You take your umbrella because its raining. 5. You drink that milk, its very hot. 6.Its dangerous, you touch that wire. 7.You be rude to your teacher. 8.In the class, you study hard.