单选题
Ice crystals do NOT immediately fall to Earth because ______.
A、
they are kept aloft by air currents
B、
they combine with other chemicals in the atmosphere
C、
most of them evaporate
D、
their electrical charges draw them away from the earth
【正确答案】
A
【答案解析】
ice crystals即是water droplets。第1段第4、5行点明题意。
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