The Chinese government _____ research into vaccine against H1N1for months, recently many have received
the first doses.

A. is doing
B. has done
C. had been doing
D. did
C
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科目：高中英語 來源：河南省期末題 題型：單選題

The Chinese government _____ research into vaccine against H1N1for months, recently many have received
the first doses.
[     ]
A. is doing
B. has done
C. had been doing
D. did

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