为何句末介词不能省略?

问题描述:

为何句末介词不能省略?
例如:Which table are they sitting (at)?
There is a big box to pack all the clothes (in).
Have you got a pen to sign these papers (with)?
另外第一句可以这样改吗:At which table are they sitting?
尤其迷惑的是第二个问题:At which table are they sitting?
可以这样说吗?

不要被疑问句弄混.疑问句不过是语序调动一下.词组是不变的.SIT AT TABLE.PACK CLOTHES IN A BOX.SIGN THE PAPERS WITH A PEN.就是这三个句子中的词组.去掉介词.意思都错.都不完整了 At which table are they sitting...