总成本包括哪些部分（）。
A、固定成本
B、可变成本
C、随机成本
D、意外支出
参考答案：A, B
________ at the theatre, he found the ticket his friend gave him was left at home. [ ]
A. To arrive
B. On arriving
C. While arrived
D. On arrived
统计活动的基本环节有（）。
A.A
B.B
C.C
D.D
E.E
