I/
1. you mustn't talk in class
2. we shouldn't break things at tet.
3. there are two playgrounds in my new school
4. a house in the city is more expensive than a house in the country
5. this dress is prettier than that one.
6. you should get up early and do exercise
7. there is no building and theatre in my hometown
8. you must do the homework
9. how many books are there in you bag?