题干

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.differenceB.comparisonC.connectionD.barrier
上一题 下一题 0.65难度 单项选择 更新时间:2013-07-23 09:24:25

答案(点此获取答案解析)