will anyone please tell me whether we always use "did" in "past indefinite interrogative" sentences...

for example in the following sentences;

1. who came?

or should it be

who did come?

2. who killed?

or

who did kill?


which one is right?

I am not sure about your terminology; i.e. 'past indefinite'.

That aside, you should use the 'who came' version. Using the 'did' construction is for emphasis.

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