Choose the correct option to complete the sentences.(1.5pts) 

1. The air has been polluted ............emissions from car engines

A. since B. because C. because of D. due of 

2. Forest fires happen too often ........the air is polluted

A. SO B. because C. since D. due to

3. Don't drink that water. It's.

A. damaged B. dumped C. clean D. contaminated

4. By the time we got to the cinema, the film. 

A. had started B. started C. starts D. starting

5. If you............ the president, what would you do to help the environment?

A. are B. had been C . were D. have been

6.A. debris B. rainstorm C. destroy D.shelter