交流电气系统及电动机故障时，应由（）处理。
A.施工人员
B.安检人员
C.持证电工
D.系统操作人员
参考答案：C
---Is that Sandy speaking?
---Sorry, she isn’t in now. She ______the cinema with her aunt.
A．has been to
B．has been in
C．has gone to
D．has gone in
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