Correct Answer: Were the return tickets to Dehradun not bought by you?

Solution : The correct choice is the fourth option .

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: " Were + plural object + prepositional phrase + past participle form of the verb + 'by' followed by the agent of the action?"

Therefore, the sentence in passive form is: "Were the return tickets to Dehradun not bought by you?"