Which of the Following Is a Feature of Vitamin D

Which of the following is a feature of vitamin D synthesis?

A) Tanning lamps and tanning booths do not stimulate vitamin D synthesis
B) Sunscreens with sunburn protection factors of 2 and above prevent synthesis of vitamin D
C) The ultraviolet rays of the sun are able to easily pierce heavy clouds and smog to promote vitamin D synthesis
D) Dark-skinned people require longer sunlight exposure than light-skinned people to synthesize equivalent amounts of vitamin D