Is it ever proper to end questions with だ? For instance:

> 誰だ？
>
> どんな食べ物は好きだ？

I have been told it was correct and incorrect by many parties, but I've always
learned to just raise the ending intonation to denote an inquiry.
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2016-10-20T23:12:34.800
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2020-06-17T08:18:27.500
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particles questions intonation
Ending Questions with だ
か is the usual way to ask a question, but it is quite acceptable to drop the か
if you use a proper "questioning" intonation. You could just say "好き?" if you
used the proper intonation.
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2016-10-20T23:27:22.523
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... 誰だ？ -- could be a regular question.

... 誰だ？ -- could be a [rhetorical question]. See [Is a sentence ending with 誰だ
but without か a question?](https://japanese.stackexchange.com/q/39693/16344)

どんな食べ物が好きだ？ -- is typical of an adult speaking to a child.

Kind-of like (in English) : [Do you like this cake?] --vs.-- [You like this
cake?]  
[Is this good?] --vs.-- [This is good?]
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2016-10-20T23:52:38.717
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2017-04-13T12:43:44.260
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Interrogative phrases ending in だ (with the exception of dialects) are used to
**_demand information_**.

As in the following:

  * 誰だ！・何者だ！ - "Who!", "Who goes there!" 
  * どこだ！ - "Where!", "Where is it!" 
  * いつだ！ - "When!", "When is it!" 
  * 何だ！ - "What!" 
  * 何のつもりだ！ - "What are you trying to do!", "What's your intention!" 
  * おい！そこでなにしてるんだ！ - "Hey! What are you doing over there!" 
  * 誰に向かって物言ってるんだ！ - "Who do you think you're talking to!"
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2016-10-21T03:05:22.357
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