O形密封圈应（）保存。
A.用铁丝穿栓悬挂
B.用密封的塑料袋
C.放在高温场所
D.放在阳光直射场所
参考答案：B
The student all the teachers were proud was accepted by Beijing University last year.
A．in whom
B．of whom
C．on whom
D．for whom
采用钢丝绳滑轮组使臂架倾俯而变幅的机构称：（）
A、刚性传动变幅机构
B、挠性传动变幅机构
C、非工作性变幅机构
whom