起升机构主要由驱动装置、传动装置、（）和安全装置等组成。
A.卷绕系统
B.取物装置
C.制动装置
D.保护装置
参考答案：A, B, C
We’re tired. We’d better have a .
A. walk B. rest C. cold
一 Will somebody go and get Dr. Smith?
一 He's already been _____. [ ]
A. asked for
B. sent for
C. looked for
D. called for
