Hii! I've been doing a lot of research to try and help you, I could be wrong but I think the answer might be A. Weight gain has more to do with the number of calories eaten than the source of those calories.
Complex carbohydrates are recommended for weight loss because they break down more slowly than simple carbohydrates, leaving you with more time to expend those calories before they break down. So, I don't believe that B. would be correct.
Explanation-wise, that's all I got. I hope any of this helps you and everyone else searching for this information. I hope you have a lovely day! Good luck (:
