So the vitamin deficiency the girl is having is vitamin D.
why? because of her diet
how? bone fractures + demographics
result? diet --> gut fiercely affects intestinal calcium absorption in the gut.
the distractor was the bone fractures and poor wound healing which wanted you to pick collagen synthesis.. which I did twice -_-.. but I think in this case of a question; when it seems too simple; explain to yourself why the other answers don't make sense.
I think I keep choosing A not realizing that vitamin C deficiency would present with lot more signs and symptoms like easy bruising and bleeding gums.