All are correct except the following: 4. "Must fat be abolished..." "Be" should come after "fat." Also, "eliminated" would sound more natural than "abolished." 7. Grammatically correct, but "environment" sounds more natural than "atmosphere."

All answers are fine, but number 3 is more natural in the active voice: Students should memorize English verbs.

Number 4 must be either: Fat must be abolished from our diets. or Must fat be abolished from our diets?

1. This medicine must be taken on an empty stomach. (must / take) 2. Your seat belt should be fastened while you are driving. (should / fasten) 3. English verbs should be memorized by students. (should / memorize) (better) Students must memorize English verbs. 4. Must fat be abolished from our diets? (must / abolish) 5. Streets ought to be repaired. They really are in bad condition (ought / repair) 6. Fish should be eaten twice a week as it is a good source of Omega 3 and vitamin D. (should / eat). 7. Batteries must be recycled to protect the environment. (must / recycle) 8. Nearly 100,000 new houses must be built every year. (must build) 9. People should be warned that there are crocodiles in the area. (should / warn) 10. Something ought to be done about global warming (ought to / do)

Muchas gracias James