补全对话（每小题1分，共5分）

Dave：Can I ask you some questions, Sally?

Sally：Sure! What’s up?

Dave：  小题1: 

Sally：Yes, it’s a little far.

Dave：  小题2: 

Sally：First, I walk to the bus station and then I take the bus.

Dave：How long do you spend on the bus?

Sally：  小题3: 

Dave：Do you need to walk after you get off the bus?

Sally：  小题4: 

Dave：How many students in your class take the bus to school?

Sally：  小题5:

Dave：Thanks a lot.

车辆从板与从板座之间的间隙比较大，是（）失效的象征。

A、车钩

B、钩锁销

C、钩尾框

D、缓冲器