TheChinesegovernment________research

发布时间：2020-07-27 16:32:39

The Chinese government ________ research into vaccine against H1N1for months, recently many have received the first doses．A.is doingB.has doneC.had been doingD.did

网友回答

C
以上问题属网友观点，不代表本站立场，仅供参考！