This article is additional to the main page dedicated to the Passive Voice.
It is not so difficult to make up questions in the passive if you those simple rules which apply to questions in the active voice.
The main rule - to put the auxiliary verb before the subject remains in the passive too.
The car was stolen. 👉 Was the car stolen?
He was taken to the hospital an hour ago. 👉 When was he taken to the hospital?
The house is being built at the moment. 👉 Is the house being built at the moment?
You need to remember when we ask a question with who, which or whom we shouldn't omit 'by'.
Who wrote that novel? 👉 Who was that novel written by?