「それがなにか」 v.s. 「それはなにか」


According to
[Weblio](http://ejje.weblio.jp/content/%E3%81%9D%E3%82%8C%E3%81%8C%E4%BD%95%E3%81%8B),
「それ **が** なにか（問題）」 is similar to "So what", e.g.

[![an
example](https://i.stack.imgur.com/SlFqW.png)](https://i.stack.imgur.com/SlFqW.png)

I'm wondering why the topic marker 「は」, as in 「それ **は** なに」, is not used here.

After all, " **As to** that, is there any thing wrong" sounds very close to
"So what".




`それがなにか` is a shorthand of `それがなにかしましたか` or `それがなにか気に障りましたか`. It roughly
translates to "Does that bother you?" or "You have a problem with that?", and
is always used defensively.

In this instance, it translates to: "I'm not married. Does that bother you?"
or "I'm not married. You have a problem with that?". The underlying context is
that in Japan, there is a social stigma against the unmarried (particularly
towards women), and the author is taking a jab at that, so to say. You
therefore have to be careful when you use this expression, as it can be seen
as being aggressive.

On the other hand, `それは何か` simply asks what it is.

**EDIT** :

> Then the question turns into: why does one not say 「それはなにかしましたか」 or
> 「それはなにか気に障りましたか」 and use 「それはなにか」 as a shorthand?

I'm not a linguist so this is how I understand it as a native speaker. By
using `が`, it refers to a concrete instance. E.g. it sounds odd to say
`太郎は何かしましたか` because `は` implies it's asking about a characteristic, yet by
asking what he did it seems to be referring to a concrete instance. It would
translate to: `Did Taro do some unspecified activity (as opposed to not doing
anything)`, which is not ungrammatical but an odd question. In contrast,
`太郎が何かしましたか` translates to `Did Taro do something specific (that bothers
you)`.

**EDIT2** :

> Is there any natural question expression that can start with 「太郎は」? If so,
> how should one discriminate the questions that should be asked with 「太郎は」
> and the questions that should be asked with 「太郎が」?

「太郎は歯を磨きましたか？」sounds very natural, but 「太郎が歯を磨きましたか？」 sounds odd (!). I don't
think I can provide a comprehensive explanation as I can't quite pin down
myself why this is. 「太郎は酒が好きですか？」 is also very natural, whereas 「太郎が酒が好きですか？」
is wrong. This question might help: [What's the difference between wa (は) and
ga (が)?](https://japanese.stackexchange.com/questions/22/whats-the-difference-
between-wa-%E3%81%AF-and-ga-%E3%81%8C) Apparently books were written on this
very subject so... Many non-native Japanese speakers I know, who practiced the
language for decades make these mistakes so I suppose it's a really hard
topic.

