If I ___________his email address, I would have sent him a message yesterday.
A. know
B. knew
C. had known
D. have known
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Only after secretary saw the train disappear in sight,_____ the railway station.
A. he lives
B. has he left
C. he left
D. did he leave
We take a great pride in our campus, _____ is one of the most beautiful university settings in the country.
A. where
B. which
C. what
D. when
We all recognize the necessity for peoplerights of others.
A. respect
B. respecting
C. to respect
D. respected
Now the pollution caused by the increasing number of car_____ more and more serious in many cities.
A. become
B. is becoming
C. became
D. had become