窄板宽拼时，每块底板的最大宽度为（）mm。
A.100
B.150
C.200
D.250
参考答案：C
设集合A={x||ax-b|＜2，a＞0}，B={x|1＜x＜5}，若A=B，求a，b的值．
I followed the man in a blue jacket thirty meters ______ me and watched him enter the hall.
A．apart from
B．ahead of
C．in the front of
D．at the back of
