问题
选择题
| 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 |
答案
答案：C
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| 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 |
答案：C