【单选题】A greenhouse is a building made of glass which is used for keeping plants warm when the outside temperature is how. In a similar way there are several gases in the atmosphere which trap(捕捉) the heat p...
A.
the way in which gases are used for keeping plants warm
B.
a natural course which is to some degree helpful to us
C.
the way' greenhouse gases trap heat on the earth
D.
the whole course in which greenhouse gases pr heat
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