Correct Answer: By whom is she taught geography?

Solution : The correct answer is the third option.

In the original sentence, "Who teaches her geography?" is in the active voice, in which the subject who is performing the action as the subject is the doer in the active voice whereas the passive voice is the voice in which the object experiences an action rather than the person that acts. Hence, the object in the active sentence becomes the subject in the passive voice.

The passive structure for the above interrogative sentence is," By +whom + is + subject + past participle form of the verb?"

Therefore, the correct option that expresses the given sentence in passive voice is: "By whom is she taught geography?"