Choose the best answer: 1. The burning of coal and gas has led ... an increase in the amount of carbon dioxide in the atmosphere. A. in. B. to. C. of. D. about. 2. Human beings should limit the use of coal ... it is the biggest source of global warming. A. and. B. however. C. although. D. as. 3. They work in groups and discuss ... should be done to reduce global warming. A. what. B. how. C. when. D. where. 4. One way to solve the problem is to ... coal with much cleaner sources of energy. A. repeat. B. replace. C. reduce. D. renew. 5. When trees are cut ..., the carbon dioxide in the air increases. A. down. B. off. C. over. D. about. 6. Cutting down the local forest ... new farmland will destroy the wildlife in this area. A. into. B. about. C. for. D. with. 7. Millions of people do not have access ... a source of water or sanitation that is likely to be safe. A. over. B. on. C. in. D. to. 8. Our planet has always had fluctuations in ... temperatures. A. point. B. average. C. standard. D. level. 9. Burning fossil fuels such as coal, oil and gas is the ... of most emissions. A. result. B. consequence. C. source. D. problem. 10. Carbon in the atmosphere from fossil fuel burning is not our ... problem. A. only. B. big. C. standard. D. important.