Correct Answer: What was done by you to help the migrant labourers during the pandemic?

Solution : The third option is the correct answer.

Passive voice is the voice in which the object experiences an action rather than the person who performs the action. Hence, the object in the active sentence becomes the subject in the passive voice.

The structure of the passive voice in the case of the simple past interrogative sentence is: " Question word + was + past participle of the main verb + 'by' followed by the agent of the action + prepositional phrase?"

Therefore, the correct answer is: "What was done by you to help the migrant labourers during the pandemic?"