斜井单绳绕缠式提升机滚筒上允许缠绕（）
A.1层
B.2层
C.3层
参考答案：B
-I hope we'll win the gold medal in the 2012 Olympic Games.
-__________. I think you're the best.[ ]
A. No, you can't
B. I bet you will
C. Congratulations
D. Thanks
轮胎起重机货物下降采用（）。
A.货物重力
B.电动机正反转
C.制动器
D.自由落体
