Who creates the challenge questions?

Answer 1

If you talking about challenge quiz then its made up by community members by submitting in quiz factory when their quizzes got approved by developers then they include in challenges
Same is for lesson factory lessons are submitted by community members when they approved they got published in the lesson section
Here are some tips to submit quizzes
https://www.sololearn.com/discuss/470195/?ref=app

Answer 2

If you are talking about quizes you can see its creator's name below the question aligned to the right.