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Hi.

I sometimes encounter the interrogative sentences in which auxiliary verbs, especially did I suppose, are omitted and verbs in past tense are placed immediately after an interrogative.

eg.
Who told you?
What happened to him?

Question:
Could you let me know if there is any grammatical rule for this usage?

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Hi,
Broadly speaking, when the interrogative pronoun (except for whom) is the subject of the question,

no auxiliary verb is used. In fact, you are questioning the subject.

Who bought this for you? He bought this for me. It is he. [subject]

What happened? A shooting incident happened. [subject]

Compare:

Whom did he choose? He chose them. [object]

What are you writing? I am writing a letter. [object]

Regards
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kook j sometimes encounter the interrogative sentences in which auxiliary verbs, especially did I suppose, are omitted and verbs in past tense are placed immediately after an interrogative. eg.Who told you?What happened to him? Question:Could you let me know if there is any grammatical rule for this usage?
When the interrogative words who, what, which, etc are used, the dummy auxiliary verb "did" is not required, as seen in your two examples. This applies to the present and past tenses. In other cases some kind of auxiliary verb is required:

In these two examples, the auxiliary verbs "be" and "can" are present in the declarative versions and they invert with the subject to form interrogatives:

Sue was fond of children. ~ Was Sue fond of children?
She can mend it. ~ Can she mend it?

If there is no auxiliary verb in the declarative, then the dummy auxiliary verb "do" is inserted, and it inverts with the subject in the same way as other auxiliaries do, such as "be" and "can" in the above examples:

Some customers complained. ~ Did some customers complain?
They go there every year. ~ Do they go there every year?

In both kinds of construction, the subject ends up in the distinctive post-auxiliary position.

BillJ
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Comments  
Thank you very much Regards for your good explanation. It's very clear to me now.
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Thank you very much BillJ for your help.
The only instance that an action verb comes after an interrogative pronoun is only 'Who' However, There are some expressions with 'What' as given in this reply. What happened, What made you to.. etc.
Hi will you give me any link or website to understand this topic better. I m really confuse in it. I understand ,what u have written but want some more example and clarification
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