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【单选题】
关于氧气瓶的使用,以下说法错误的是A.
氧气瓶附件有缺损，阀门螺杆滑丝时，应停止使用
B.
氧气瓶不能强烈碰撞，禁止采用撞击的方法进行装卸或搬运
C.
操作者的双手、手套及工具不得沾染油脂
D.
氧气瓶内的氧气可全部用完
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皮皮学刷刷变学霸
举一反三
【单选题】I don't know____yesterday. [ ]
A.
what he happened
B.
what did he happen
C.
what happened to him
D.
what has happened
【单选题】What does the sentence 'The air helps purify the water' illustrate?
A.
The ecological balance.
B.
The water cycle.
C.
The earth's limited resources.
D.
The life cycle.
【单选题】I didn't know what ____ to her last night. [ ]
A.
was happened
B.
happening
C.
happened
D.
was happen
【单选题】I don’t know _____.
A.
what happened to him
B.
what did he happen
C.
what he happened
D.
what was the matter
【单选题】-----What _____? -----I______my key and can't open the door.
A.
happened, lost
B.
has happened, lost
C.
happens, have lost
D.
has happened, have lost
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