I need some help with んです/ので/ん


I was studyng from a book and I can't answer this question (and I don`t have
the answers) the question is: **普通の言い方に直すとどうなりますか。**

  1. 私に **予約してくれんか。**

a)予約してくれないのですか。 b)予約してくれるのですか。 c)予約してくれませんか。

To me all of the answers are the same :(




The ん in 予約してくれ **ん** か is a contracted form of ない. Thus, the sentence is the
same as 私に予約してくれ **ない** か. The polite version of this sentence is
私に予約してくれませんか, so I think the answer is **c)**. (I hesitate to call the polite
form 普通の言い方, though...)

The other options contain
[explanatory-の](https://japanese.stackexchange.com/q/5398/5010), but it is not
included in the original sentence. 予約してくれないのですか means "(Does that mean) you
aren't going to make a reservation for me? (That's disappointing!)".
予約してくれるのですか means "(Does that mean) you are going to make a reservation for
me?" These are not simple requests.

To distinguish the two types of ん:

  * ん after the "pre-nai" form of a verb is a contraction of ない. 

> 食べない → 食べん  
>  要らない → 要らん

  * ん after the dictionary form (or more precisely, the attributive form) of a verb is a contraction of の. 

> 食べたのだ → 食べたんだ  
>  要るのです → 要るんです

