94204
If not, what would the sentence be if I want to ask "Where is B?"
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2022-04-20T22:52:16.887
94199
2022-04-21T02:42:57.853
51140
question
grammar
Can "Bはどこですか" be the question of "AにBがあります"?
Ｂはどこですか is certainly an appropriate way to ask “Where is B?” What is not
appropriate here is ＡにＢがあります as a response to that question.

> 本はどこですか  
>  Where is the book?
>
> ? テーブルの上に本があります。  
>  ? There is a book on the table.

Two pieces of information are involved here.

> A: place
>
> B: object

The first person knows what object he is asking about and also assumes the
other person will understand what it is he is referring to. What he doesn’t
know is where it is located. In other words, the object is known and the place
is unknown. This is why he puts forward the object (本) as the topic of the
sentence, marking it with は, and uses the question word for “where” (どこ) where
the place is expected.

The response, on the other hand, marks the object with が. This makes it sound
like the object (本) is the new information, rather than the place (机の上). The
sentence is understood as talking about the existence of an hitherto unknown
object in a particular (possibly already known) place, rather than the
whereabout of a known object as expected from the question.

The response should be either

> （本は）テーブルの上です。  
>  It (= the book) is on the table.

or

> （本は）テーブルの上にあります。  
>  It (= the book) is on the table.

Note that the object (本) is marked with は as it was in the question. Since it
is already established as the topic of the dialogue, 本は can be omitted
altogether. In fact, the response sounds more natural when it is omitted
unless there is some reason to emphasize it, for example when you want to put
the book in contrast with something else that is in some other place.

Ａに何がありますか is asking what is in a particular place. The place is known and the
object is unknown. Hence the question word for “what” (何) where the object is
expected.

> テーブルの上に何がありますか。  
>  What is on the table?
>
> （テーブルの上に）本があります。  
>  A book is (on the table).

本, which is marked with が, is the new information in the response.
CC BY-SA 4.0
2022-04-21T02:42:57.853
94204
2022-04-21T02:42:57.853
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answer