题目

Lucy usually has lunch at school.(改为一般疑问句) Lucy usually lunch at school? 答案：【1】Does【2】have已知椭圆+=1的左右焦点为F1、F2，P为椭圆上一点，O是坐标原点，M是PF1的中点，若|PF1|=4，则|OM|=    ．