For a history test my novel character takes, is there any way I can legally use questions from online study materials, perhaps with rewording?

You can't copyright an idea.

You can copyright specific text.

If you are unable to take a written test you use as an example to come up with the same ideas expressed in your own words then you need to do more work on your writing skills.

A hint, ChatGPT often copies text from original sources verbatim. That makes ChatGPT unfit to generate text for your novel. You can still use ChatGPT as a source of ideas, just not as a source for text.