电力系统中电气装置保证正常运行需要所设的接地称为（）。
A.工作接地
B.保护接地
C.雷电保护接地
参考答案：A
The energy gained from the sun can then be used during the night to enable the necessary chemical reactions to ______ in his body.
A．precede
B．proceed
C．progress
D．practice
半镇静钢
