飞机起飞后前轮如何定中（）
A.定中凸轮定中；
B.转弯作动筒定中；
C.齿轮齿条定中
参考答案：A
— I drove to Zhuhai for the air show last week.
— Is that ____________ you had a few days off?
A．why
B．when
C．what
D．where
炉子剧凉，（）涌渣时，应迅速打开渣口放渣，严防烧穿。
