控制系统是指由（）组成的具有自身目标和功能的管理系统。
A.控制主体
B.控制客体
C.控制信息
D.控制措施
参考答案：A, B, C, D
Her childhood dream became a ______ when she broke the 100m race world record. [ ]
A. truth
B. fact
C. reality
D. certainty
Persons under 18 _____ not be employed in night work in the US.
A．can
B．may
C．will
D．shall
