当循环水泵运行时，供水管上各点压力总水头的连线称为( )。
A．供水管动压头线 B．供水管静压头线 C．供水管动水压线 D．标高线
参考答案：C
完成句子。
1. There is ______ (毫无疑问) he will come on time this afternoon.
2. You are ______ (有危险) putting on your weight.
3. ______ (说实在的), I didn't mean to hurt him.
4. The twin brothers a lot ______ (有共同之处), and get on very well.
5. I like ______ (戏弄) others but don't like to be laughed at.
化简：-[-（2a-b）]=______．
