道路交通事故中，在来车方向距事故现场( )m处竖立警告标志，防止其他车辆进入事故现场。
A．100 B．150C．200 D．250
参考答案：A
—Your father’s birthday is coming. Why don’t you get him a pair of glasses?
—_______. Glasses can help him see better.
A．That’s too boring.
B．That’s not creative enough.
C．That sounds great.
D．That’s not necessary.
造成加热炉回火的原因及现象是什么？怎样预防？
