Yes, I agree with you. It's not very good at all. I would change it to:
1. It is clear from the passage that, among writers of non-fiction, there is a great variety of aims – one of which is the desire to please.
(Or you might put a comma, semi-colon, or colon instead of the dash.)
I'm sorry to see yet another dodgy exam question.
All the best,
- For Teachers