发生错误操作隔离开关,当已出现电弧时,应(),尽量避免事故扩大。
A.立即拉开隔离开关
B.立即合上隔离开关
C.立即停止操作
D.操作人紧急撤离现场
参考答案:B
—Helen, where is your homework?
—Sorry, Miss Read. I _______ some of it last night. But I haven't finished doing it yet. [ ]
A. do
B. did
C. have done
D. will do
趋势线是什么?