After Her Last Check-Up, Harriet Was Informed That Her Active

After her last check-up, Harriet was informed that her active Vitamin D levels were low. Which of the following conditions may explain why this is so?

A) Melanin production has increased due to sun exposure, reducing Vitamin D activation.
B) Liver dysfunction has reduced the conversion of cholecalciferol to the intermediate for calcitriol production.
C) An increase in Vitamin D absorption at the intestines has overwhelmed the homeostasis of vitamin production at the kidneys.