柱混凝土分层浇筑时，振捣器的棒头须伸入下层混凝土内（）。
A.5~10cm
B.5~15cm
C.10~15cm
D.5~8cm
参考答案：A
电能表装接不合理，造成少计或漏计电量有那几种原因？
_______ the Internet is of great help, I don’t think it’s a good idea to spend too much time on it.
A．If
B．While
C．Because
D．As
