CD對(duì).
由“小車和木板一起沿光滑平面做加速運(yùn)動(dòng)”,知它們是相對(duì)靜止的,車與木塊之間的摩擦力是靜摩擦力,不能用 f＝u*Fn來(lái)算.A項(xiàng)錯(cuò).
B項(xiàng)錯(cuò),這個(gè)較明顯.
C項(xiàng)對(duì),對(duì)車和木塊這個(gè)整體有　F＝(M+m)a,對(duì)木塊有 f ＝ma,二式聯(lián)立得 f ＝（mF)/（m+M).
D項(xiàng)對(duì),對(duì)車有　F合＝F－f＝Ma.