问题
选择题
More and more people have realized 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
答案
答案：D
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More and more people have realized 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
答案：D