what gave you the idea?想法来自哪里?/什么让你产生这个想法?/灵感来源哪里?
what在这里是主语从句中的主语,试比较who gave you the idea?
what did you give the idea?该句不通,无法成立.如果改成陈述句：you gave the idea what(这是什么成分?)能成立么?