Choose the correct answer A, B, C, or D. 1. In the future, many cars will run ________ electricity, which doesn’t cause air pollution. A. in B. on C. by D. with 2. You should turn the tap ________ when you brush your teeth to save water. A. up B. down C. on D. off 3. You should donate your old clothes, toys and furniture to people in ________. A. order B. fact C. need D. case 4. ________ robots can help to teach children in the classroom, they will never replace teachers. A. When B. Although C. Because D. If 5. There are lots of ________ problems nowadays, mainly because of pollution. A. natural B. social C. practical D. environmental 6. To ________ waste we should avoid buying products with a lot of packaging. A. recycle B. reuse C. reduce D. remake 7. ‘Will robots be more and more expensive?’ ‘_______ Prices will become cheaper over time.’ A. Not at all. B. Sure. C. Sounds great! D. I think so. 8. The Amazon River is ________ river in the world. A. the wider B. wider than C. the widest D. widest