21. Renewable energy  is also called”____________energy” because it doesn’t pollute the air.

A. inexhaustible        B. available                 C. clean                 D. dangerous

22. ____________ the pollution it cause, coal still plays an important role in the production of electricity around the world .

A. Despite                  B. Due to                     C. Even though            D. However

23. What ________if  carbon dioxide levels continue to increase?

A. happen                    B. will happen                    C. will be happened  d. will be happening

24. The use of wind energy is growing rapidly because it is widely available and______ .

A. environmental friendly                                         B. environmental friendly

C. environment friendly                             D. friendly environmental

25. Using solar panels at home can help______ your electric bill and your carbon footprint.

A. reduce                   b.  increase               C. provide                              D. convert

26. Wind power is the most promising_______ source of energy.

A. non-renewable      B.   natural                C. limited                             . alternative

27. You can save much water by_______ .

A. using energy saving light bulbs              B. using biogas for cooking

C. taking showers instead of baths              D. walking or riding a bike to school

28. ‘Is it difficult to reduce our carbon footprints?’ ‘________________’

A.   It depends on the way you think.              B. Not at all. Just practicing the 3R’s.

C. It’s not if we still rely on fossil fuels.             D. I’m not sure. What will happen?