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
