Bài 15 : Điền must/ mustn’t/ don’t have to/ doesn’t have to/ have to/ has to vào chỗ trống sao cho phù hợp. . You ... ....................worry about her! She's all right now! 2. He's very ill, he................ stay in bed. . Children .................... play in this dangerous place. 4. We are on Saturday! We........................ to get early! 5. You ................. smoke here! It's a school! 6. Old people.................. be helped. 7. You ................... forget your dictionary for the exam !8. She....................... choose if she doesn't want to! 9. They are happy because they...................... wear a uniform in their new school. 10. The river is too deep, you.............................. swim here!