两辆汽车在同一平直路面上行驶,它们的质量之比为m1:m2=1:2,速度之比v1:v2=2:1,当两车急刹车后,甲车滑行的最大距离是S1 , 乙车滑行的最大距离是S2 , 设两车与路面间的动摩擦因数相同,不计空气阻力.则() A . S1:S2=1:1 B . S1:S2=4:1 C . S1:S2=1:2 D . S1:S2=2:1 答案:BIt’s wise _________ you _________ out that difficult problem. A. for, to work B. of, working C. to, working D. of, to work