Par qui a été inventée cette machine ?

English Translation

By whom was this machine invented?

“C’est qui” works too.

Are you sure? To transform from passive to active I think you would have to change more of the sentence, like “Celui qui a inventé cette machine, c’est qui ?”.

Disclaimer: I’m very far from being good at French.

C’est qui qui a inventé cette machine ? is acceptable and a common, albeit inelegant, phrasing.

I agree, “C’est qui qui…” is indeed “inelegant” :slight_smile: .

I think a simpler option would be: “Qui a inventé cette machine?”, just like “Who invented this machine?” would work just fine in English.