Trees and flowers _______ every year to make our school more beautiful.

曾经有人问闻名世界的指挥家卡拉扬：“你是如何指挥世界著名的交响乐团的？”卡拉扬说：“我只强调三个音，来使我的乐队变成团队。首先强调起音，起音不齐，乐曲就乱。第二是个人的专业音，要弹奏出最出色的音。第三个音是团队音，当你打出自己的专业音后，还要考虑到整体，是不是会干扰别人的音。”

小明用30N的水平推力使箱子沿水平地板匀速滑动，箱子受到的摩擦力是____ N；在箱子上放一袋面粉后，小明要加大力气才能推动箱子，原因是箱子对地板的____增大，导致摩擦力增大．

一个正多边形的每个外角都等于20°，则这个正多边形的边数是​____．

增加：在缺词处加一个漏字符号（∧），并在此符号下面写出该加的词。

删除：把多余的词用斜线（＼）划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1）每处错误及其修改均仅限一词；

     2）只允许修改10处，多者（从第11处起）不计分。

    It is known that some students cheat in exams. There are three reason. First of all, there are so many exams. Beside, the exams given are difficulty in some ways. Secondly, some students have to cheat in exams because of they are too lazy.The last reason is to please our parents and teachers.For some students,low marks brought them great pressure and make them depressing.In my opinion,cheating in exams are wrong.We should take active attitude to our studies,and try to get a mark what is true.