Dưới đây là các câu được viết lại dựa vào từ gợi ý:

4. There **is a higher birth rate than** death rate that can cause overpopulation.

5. We have several ways **of producing energy** without destroying the environment.

6. We should **build more green schools** in Vietnam.

7. After **David had gone home**, we arrived.

8. Before **we took a look around**, we had lunch.

9. When **the light had gone out**, we got out of the office.

10. By the time **she had explained everything clearly**, we started our work.