属于旅游安全重大事故的标准是()。
A.经济损失100万以上
B.经济损失10至100万
C.造成旅游者死亡多名
D.多人重伤致残
参考答案:B, D
Your job ________ for your return. [ ]
A. will be kept
B. will keep
C. had kept
D. had been kept
保护接零的首要作用是故障时迅速切断故障设备的电源。