1. Keeping the environment clean is very important.

=> It's....................................very important to keep the environment clean............................................................

2. Old car tires are recycled to make shoes and sandals.

=> People.................................recycle old car tires to make shoes and sandals........................................................

3. It's three months since I last spoke to Mr. Quang.

=> I haven't..........................spoken to Mr.Quang for three months...............................................................