15. Some of the tunnels in the cliff are totoally natural; some others were carved out by soldiers  for defensible purpose

14. His parents don't allow him staying out late on weekdays.

13. Each student have to write a paragraph about the benefits of learning English.

12. Many living organisms depend largely on the environment for the satisfaction of its needs.

11. Jane help her mother to do the housework when she has free time.

0. Working as a doctor would give me a chance taking care of people's health.

9. A number of wildlife habitat reserves have been established in order to saving  endangered species from extinction. 

8. Children learn primarily by directly experiencing the world around it

7. She always try to finish her homework before going to bed.

6. My mother always get up early to prepare breakfast for everyone in the family