在线电压为220v的工频三项电网中，两相触电时，人体承受的电压（）。
A.为220V
B.为380V
C.为110kv
D.与距离有关
参考答案：B
It was on July 1, 2006 ___ Qinghai-Tibet railway began operation, ____ is a symbolic project in
China's West Development Strategy.[ ]
A. when; that
B. that; when
C. which; when
D. that; which
“商品”与“顾客”两个实体集之间的联系一般是______。
A．一对一
B．一对多
C．多对一
D．多对多
