Final answer:
Cholecalciferol is a precursor for vitamin D, which is synthesized in the skin and then activated in the liver and kidneys. It is essential for healthy bones due to its role in calcium and phosphorous absorption.
Step-by-step explanation:
Cholecalciferol is a precursor for vitamin D, not vitamin A, vitamin E, or vitamin K. When exposed to UV radiation, particularly from sunlight, the skin synthesizes cholecalciferol. It is then converted by the liver to calcidiol and subsequently into calcitriol in the kidneys, which is the active form of vitamin D. This vitamin is crucial for the absorption of calcium and phosphorous, essential for maintaining healthy bones. Regarding water-soluble vitamins, the correct answer is vitamin C, which is different from the fat-soluble vitamin D.