1. Keeping the environment clean is very important.

→ It’s very important to keep the environment clean.

2. They will show the time machine to the public when they finish it.

→ The time machine will be shown to the public when it is finished.

3. He was delighted to receive his aunt’s letter.

→ He was delighted that his aunt sent him a letter.
4. Old car tires are recycled to make shoes and sandals.

→ People recycle old car tires to make shoes and sandals.
5. I’m very sad that I wasn’t accepted in that group.

→ I’m very sad not to be accepted in that group.

6. It’s three years since I last spoke to her.

→ I haven’t spoken to her for three years.

7. Tam doesn’t type as fast as she used to.

→→ 7. Tam used to type faster than she does now.

8. “ Please turn down the radio for me”, said my father.

→ My father asked me to turn down the radio for him.
9. Lan will be fifteen next week.

→ It is Lan’s fifteenth birthday next week.

10. How long is it since you used the pen?

→ When did you use the pen?