為什麼這句子at the end用的是at,on the right side用的是on?多謝!?

除了"習慣"以外,其實是沒什麼好解釋的了!

習慣上,at 用在"比較精確"的點.
習慣上,on 用在"比較模糊"的邊.
習慣上,in 用在"更是模糊"的區.

但是,這些都是習慣上.例外是有一堆.
例如說: in the end, she married another man.裡面的"in the end"是使用在"抽象的"點.

at--prep:-(place and direction),; indicating the place in or near which something is; at my room at the end of the corridor. at the idea of going to the end of the corridor.
on prep:-attached to, forming part of a surface, lying against; in contact with; a room on the right side---If indicating direction towards=turn yourself on the right---If indicating proximity接近,靠近;附近 close to=a room on the right side, not on both sides of the corridor--just on the right-hand-side--->-on the right side.
Hence your room is at the end of the corridor on the right side.