[填空题]A over the past 50 years
B beneath the earth surface
C by more than 50 percent
D for more than four decades
E as a raw material
F for families
Natural gas is recognized as the most economical energy source______.

[填空题]A over the past 50 years
B beneath the earth surface
C by more than 50 percent
D for more than four decades
E as a raw material
F for families
Natural gas is stored deep______.

[填空题]Natural gas is stored deep______．

[单项选择]A. over past 50 years B. for more than four decades C. by more than 50 percent D. for home energy use E. as a raw material F. beneath the earth’s surface Natural gas is stored deep

[单项选择]

The amount of sunlight reaching Earth’s surface appears to be growing. The phenomenon, which some dub "global brightening," (1) scientists with a puzzle. If the (2) is real and global, how long will it last and what are the consequences for climate change, the planet’s water cycle, and other (3) that draw energy from sunlight (4) , the answer might seem obvious: More sunlight reaching the ground in a warming world means that temperatures will get warmer (5) . Not so fast, some researchers say. Additional warming would be certain (6) nothing else in the climate system changes. And the climate system is (7) static. Some combinations of changes could reinforce the heating; others could (8) it. Unraveling these interactions and forecasting their course require an accurate accounting of the sunlight reaching the surface and the (9) the surface sends skyward. Moreover, researchers say, measurements of
A. ongoing
B. outgoing
C. incoming
D. upcoming