在（）中，应该采用保护接零方式。

A.中性点有良好接地的低压配电系统

B.中性点不接地的低压配电网络

C.农村配电网络

D.高压电气设备

Atmosphere laden with coal dust or grain dust caused by loading these cargoes（）.

A.require loading operations to be shut down until the atmosphere clears

B.are toxic to human life

C.are subject to spontaneous combustion

D.may be explosive in some concentrations