1.It's very important to keep the enviroment clean.
2.The time machine will be shown to the public when they finish it.
3.He was delighted that he received his aunt's letter.
4.People recycle old car tires to make shoes and sandals.
5.I'm very sad not to be accepted in that group.
6.I haven't spoken to her for three years.
7.Tam used to type faster than now.
8.My father asked me to turn down the radio for him.
9.It's Lan fifteen birthday next week.
10.When have you used the pen?
