麻痹性肠梗阻病人常首先发生（）
A.低渗性脱水
B.高渗性脱水
C.等渗性脱水
D.水肿
E.水中毒
参考答案：C
He ___________ the volunteer group last year and ___________ many activities since then.
A. took part in…joined B. joined…took part in C. joined…has taken part in
在接地网中，带有保护接地的电气设备，当发生相线碰壳故障时，若人体接触设备外壳，保证不会发生触电事故。
