some students even have no ideal of ^_they are studying ,so they waste much time playing

题目

some students even have no ideal of ^_they are studying ,so they waste much time playing
为什么用why 而不是what

答案

后半句说了“所以他们（学生）浪费很多时间去玩耍.”
根据意思可以推断出来前半句是说学生不理解为什么要学习.
如果用what,学生不理解在学什么,跟后半句不符,也不符合常识.