估价目的
参考答案：
一个估价项目是为何种需要而进行的。
Do you know what ______ the little boy? [ ]
A. happened has to
B. happened with
C. has happened to
D. have happened
功率因数低，说明电路用于交变磁场转换的无功功率大，从而降低了设备的利用率，增加了线路供电损失。
