问题
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
B:scientists have known
C:have scientists known
D:had scientists known
正确答案是：
同类题型
I will carry out the plan _____ there is much difficulty ahead
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I used to_________up very late,but now I’m getting used to_____up early.
Rosa _____ this washing machine for more than ten years. She is thinking about buying a new one.
Attention, please. The plane to London _______ off at 9: 00.