作自转接地时，最合适的操纵是（）。
A.接地时，机头稍微上仰
B.接地时应垂直下降
C.接地时向后拉驾驶杆使直升机缩短滑跑距离
参考答案：C
Mary is so wet. She _______ in the rain.
A．must be caught
B．must have been caught
C．should have been caught
D．can have been caught
收入支出表一般以（）为一个编制周期。
A．1个月
B．6个月
C．6个月
D．12个月
