It would be that "d. Muhammad was engaged in long-distance trade where he came into contact with monotheists" that likely would have influenced his acceptance of monotheism, since this allowed for him to gain new and challenging points of view.
I think the answer is D, I might be wrong though but hope I helped! Sorry if I didn't!
Answer:
you can use history.com or britannica.com i use those websites when doing social studies as well. or you can use lumenlearning.com
Explanation:
hope this helps :)