Correct Answer: Art classes for children were being taken by a ten-year-old girl.

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 voice becomes the subject in the passive voice.

The structure of the passive sentence in the past continuous tense is object + were + being + past participle form of the verb + by + agent of the action .

Therefore, the correct sentence is: Art classes for children were being taken by a ten-year-old girl.