题目

There will be the 18th sports meeting of No. 2 High School next month. The students are busy _____ it.A. to prepare for B. preparing forC. to preparing for D. prepare 答案：【答案】B【解析】句意：下个月二中将举行18届运动会，学生正忙着为它做准备。根据be busy doing sth.“忙于做某事”， prepare for为……做准备；故选B。仔细观察图1，说明力的作用效果不仅跟力的大小、方向有关，还跟力的    有关；观察图2发现，将滑动变为    的方式可以减小摩擦．