Question

voice change-who did this?​

Answer 1

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By whom was this done ?

Explanation ↴

In the given sentence, the structure is complicated because it's an interrogative sentence. So, we have to change the order of the sentence by changing the subject, verb, and object order.

It would start with 'By whom', because 'who' changes to 'whom' in passive voice. Then, the verb 'was done' will be broken up by the word 'this'.

Note ↴

Identify the parts of speech and place them correctly in the interrogative form to get the correct answer and don't forget to use a question mark "?" at the end of the sentence.