25. Which of the following are the three main energy sources used in the U.S?
26. The majority of Earth's energy input comes from:
27. _________ is an example of a fossil fuel; _________ is an example of an alternative energy source; and _________ is an example of a renewable energy source:
28. The Alaska National Wildlife Refuge (ANWR) has made headlines because of:
29. Which of the following is the strongest argument in favor of pollution allowance trading:
30. Oil is: