Question

What do you do at night ?
( change into passive voice ).

Answer 1

Answer:

What at night is done by you?

Answer 2

Normal structure of ‘wh’ questions in active voice is-

‘Wh’ word + auxiliary + subject + verb + object ? (Active Voice)

While changing the sentence into passive, this structure becomes-

‘Wh’ word + auxiliary + subject + V-3 + by + agent ? (Passive Voice)

Thus the answer must be-

What did you being doing at night?

(I guess)