题目

Many students believe that the choice of their courses and universities should ________ their own interest. A . be based on B . base on C . be basing on D . base at 答案：A如图，有长为30m的篱笆，一面利用墙围成中间隔有一道篱笆（平行于AB）的矩形花圃．设花圃的一边AB为xm，面积为ym2．（1）求y与x的函数关系式；（2）如果墙的最大可用长度为10m，要围成面积为63m2的花圃，AB的长是多少？