问题描述：
More amd more people have realised we won't have cleaner water to drink unless something _____ soon
A.was done B.will be done C.to be done D.is done
请详细讲讲,另外,be done在这里是什么意思
A.was done B.will be done C.to be done D.is done
请详细讲讲,另外,be done在这里是什么意思
问题解答：
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