液压传动的起升机构中，高速液压马达传动需要通过（）带动起升卷筒，具有重量轻、体积小等特点。
A、齿轮
B、离合器
C、联轴器
D、减速器
参考答案：D
There was a sign near the entrance _____ the library. [ ]
A. to
B. of
C. in
D. at
---- Do you know Tom, ______ father is an engineer?
---- Yes, quite well. He ______ be the first to offer me help when I met with problems.
A．the; would
B．which; used to
C．that; used to
D．whose; used to
