题目

如图所示,物体B的上表面水平,当A、B相对静止沿斜面匀速下滑时,斜面保持静止不动,则下列判断确的是( ) A . 物体B的上表面一定是粗糙的 B . 物体B，C都只受4个力作用 C . 物体C受水平面的摩擦力方向一定水平向右 D . 水平面对物体C的支持力等于三物体的重力大小之和 答案：B2．Kate：Good  moming，Jack．（51）EJack：Oh no!Kate：What do you mean，"Oh no"？Jack：I think I left it--on the kitchen table!1 was hurrying because l was late．Kate：（52）GJack：I'm very sorry!Kate：Well，it doesn't matter．（53）CBut can you  bring it tomorrow？Jack：Yes，OK．I'm sorry!Kate：It's all right．See you tomorrow．…Oh，Jack，What's the matter？（54）B．Jack：Well，I remember your book isn't at home．I think I left it on the bus!Kate：Oh，my god!（55）A．A．You lost it!B．You look strange．C．I can share with Judy in class．D．Biology is my favorite subject．E．Have you got my biology book？F．Do you think it is in your schoolbag？G．But I've got a biology lesson this afternoon!