They were ahead during the first half of the match, but they ________ in the last five minutes．

A．were beating

B．beat

C．were beaten

D．had been beaten

在施工现场专用的中性点直接接地的电力线路中，必须采用（）接零保护系统。

A、TN-C

B、TN-C-S

C、TN-S

D、TT