英语单选题:More and more people have realized that we will not have cleaner water……

问题描述:

英语单选题:More and more people have realized that we will not have cleaner water……
More and more people have realized that we will not have cleaner water to drink unless something ______ soon.
A.was done
B.be done
C to be done
D.is done

.D unless引导的条件状语从句,主句是将来时,从句中用一般现在时或现在完成时代替一般将来时.