II. Complete the following sentences. Use affirmative or negative of "must". 1. You __________________________ study harder to get better marks. 2. The boy is only twelve years old. He ___________________________ ride a motorbike. 3. Jimmy, you __________________________ bite nails. 4. My classmate is very ill. She __________________________ see a doctor as soon as possible. 5. Your hands are dirty. You __________________________ wash them before meal. 6. We __________________________ brush our teeth at least once a day. 7. Children __________________________ play with dangerous objects like knives and matches. 8. Students __________________________ use mobile phones during the test. 9. Babies ___________________________ go to bed early. 10. You ____________________________ be impolite to elderly people.