Only when all the fish in the lake died ________ how serious the pollution was.[

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Only when all the fish in the lake died ________ how serious the pollution was.[     ]
A. did the villagers realize
B. the villagers realized
C. had the villagers realized
D. the villagers had realized

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举一反三

Only by introducing scientific management, I suppose, ________ our company to a bright future and
make more profits in the next years.[    ]
A. can we bring
B. we have brought
C. we can bring
D. have we brought

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Only when ________ be possible to sign the papers.[ ]
A. does the boss come will it
B. the boss comes will it
C. has the boss come it will
D. the boss comes it will

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To our surprise, not a single word ________ in the discussion last Friday. [     ]
A. had the teacher said
B. said the teacher
C. the teacher had said
D. did the teacher say

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______ allow drugs to become uncontrolled in our district. [ ]
A. In certain circumstances can we
B. In no circumstances we can
C. Under any circumstances we can
D. Under no circumstances can we

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We have to admit that never in the past twenty years ________ so greatly as before.[     ]
A. did the city change
B. the city has changed
C. has the city changed
D. the city had changed

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