氧气钢瓶通气管道及操作者身上不能带有(),以防氧气冲出,造成燃烧和爆炸事故。
A、机器
B、设备
C、车头
D、油脂
参考答案:D
.Mr.Smith was_________ to be a doctor but he became a teacher when he grew up.
A.demanded
B.supposed
C.suggested
D.agreed
原位癌