Little_____ about A-H1N1 so far, so there is no doubt that many people are afraid when talking about the disease.
A.did scientist know | B.scientists have known |
C.have scientists known | D.had scientists known |
推荐套卷
Little_____ about A-H1N1 so far, so there is no doubt that many people are afraid when talking about the disease.
A.did scientist know | B.scientists have known |
C.have scientists known | D.had scientists known |