Your backpack is on the chair.对on the chair 部分提问
问题描述：
Your backpack is on the chair.对on the chair 部分提问
答
Is your back on the chair?
Yes, it is. 这个肯定是错的，对划线部分提问不能有划线部分的。
应该是 Where is my backpack?
答
Where is my backpack?
答
Where is my backpack?
On the chair是地点,对它提问,应该用where