the boy didn't know_____ .a.which chair to sit on b.which chair to sit选 A对吧.CHAIR做宾语,所以加ON
问题描述：
the boy didn't know_____ .a.which chair to sit on b.which chair to sit选 A对吧.CHAIR做宾语,所以加ON
答
A sit 是不及物动词,所以后面还要加 on
如果动词是seat,就应该选B了