Dùng gợi ý viết lại các câu sau sao cho nghĩa của câu không thay đổi

Dùng gợi ý viết lại các câu sau sao cho nghĩa của câu không thay đổi 
1. Keeping the environment clean is very important.
=> It's..........
2 They will show the time machine to the public when they finish it.
=> The time machine..........
3. He was delighted to receive his aunt's letter
=> He was delighted that.........
4.Old car tires are recycled to make shoes and sandals.
=> People.............
5. I'm very sad that I wasn't accepted in that groy
=> I'm very sad not.........
6. It's three years since I last spoke to her
=> I have't ......
7. Tam doesn't type as cast as she used to
=> Tam used ........
8." Please turn down the radio for me" said my father.
=> My father asked.........
9. Lan will be fifteen next week
=> It is lan's .......
10. How long is it since you used the pen?
=> When..........