Question

what did he do ? voice chnge​

Answer 1

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What was done by him ?

Explanation ↴

To turn active sentences beginning with 'wh-words' into passive ones, the appropriate forms of the 'be' verbs are placed after the 'wh-words' (Except: which) and the main verbs (the finite verbs) of the sentences are changed into its past participle form.

After that the 'subject' in the active voice becomes the 'object' in the passive voice and It is generally preceded by the preposition 'by' and a question (?) mark.