Which vitamin helps activate calcium absorption in the body?

Urinary system...this doesnt sound right to me..anyone got any imput?

Personally, I believe it's the endocrine system because hormones often activate vitamin D. Also, the integumentary system helps with the absorption of vitamin D and activates it as well.

Thanks for your timely reply. I am completing an A & P assignment which asks me to choose from a list of key answers. All the others have been used, and the two remaining answers are a choice of either the reproduction or urinary systems. My guess is that the answer is ... a repeat of an answer before.