液压传动可以在较大速度范围内实现()。
A、有级变速
B、无级变速
C、恒速
参考答案:B
----- As we know, you won’t go back to the USA since you have established a research center here.But how long _____ in America?
----- For almost 10 years.
A.did you study
B.have you studied
C.were you studying
D.have you been studying
增强文化整体实力和竞争力要坚持把()放在首位。
A.构建现代文化产业体系
B.社会效益
C.文化产品的丰富
D.经济效益