在光滑的水平冰面上，质量为的木块B处于静止伏态．质量的小木块A静止于B上．如图所示．A与B间的动摩擦因数为μ．今有一小球从水平方向自左向右飞来撞击木块A后反向弹回，而A获得了相对于冰面的速度，B的速度仍可视为零．问木块B的长度至少为多长，木块A不致滑落到冰面上?(木块A可视为质点)

This printer is of good quality. If it ________ break down within the first year, we would repair it at our expense.

A．would

B．should

C．could

D．might