The correct answer is rewrite the sentence as a question.
The difference between an active and a passive sentence is that in the active one, the subject is performing an action, and in the passive one, it is receiving a particular action. So this means that you need to move the actor and the receiver to their new respective positions, but also completely revise the structure of the verb into a passive one.
For example:
John is writing a letter. (active)
A letter is being written by John. (passive)
What we do not need to do is create a question - a question can still be either active or passive, so that wouldn't change anything.