货船常采用哪种舵（）
A.平板舵
B.双支点平衡舵
C.半悬挂式平衡舵
D.B或C
参考答案：D
我国政治、文化中心是[ ]
A、天津
B、北京
C、上海
D、广州
There _____ no use to ask him this question.[ ]
A. were
B. is
C. are
D. was
