当电压为220kV时，塔式起重机和输电线路之间的安全距离沿垂直方向为（）m。
A、6
B、5
C、4
D、3
参考答案：A
Consumption of the total life-cycle effort in software maintenance is ______ that in software development.
A．less than
B．larger than
C．equal Or less than
D．equal or larger than
在水中遇到鲨鱼，落水者可主动攻击鲨鱼的鼻子。（）
