Carbon dioxide,which makes a________between us and the sun,prevents heat from getting out of the atmosphere easily,so the earth is becoming warmer.
A.difference | B.comparison |
C.connection | D.barrier |
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Carbon dioxide,which makes a________between us and the sun,prevents heat from getting out of the atmosphere easily,so the earth is becoming warmer.
A.difference | B.comparison |
C.connection | D.barrier |