如果F是Fl和F2的合力，则反映它们之间关系的图中正确的是（）
A.
B.
C.
D.
参考答案：B
Mary was caught in a traffic jam and by the time she arrived at the airport her father’s plane_______.
A．took off
B．had already taken off
C．was take off
D．had already been taken off
( )系统能生成各种内部报表，外部报表及汇总报表。
A．账务处理 B．工资核算 C．账务分析 D．报表
