鞋底部结构主件有哪些？
参考答案：
内底、外底、中底、鞋跟。
_____, the car stopped all at once.
A．Seeing a boy lying on the ground
B．On seeing a boy sitting on the road
C．The driver saw a boy standing on the road
D．The minute the driver saw a boy seated on the road
钻床变速前应（）。
A、停车
B、取下钻头
C、取下工件
D、断电
