Which vitamin is classified as fat-soluble?

The correct answer highlights Vitamin D as a fat-soluble vitamin, which is important for a variety of bodily functions. Fat-soluble vitamins, including Vitamins A, D, E, and K, are absorbed in the intestines along with dietary fat and can be stored in the body's fatty tissues and liver.

Vitamin D specifically plays a critical role in calcium metabolism, bone health, and immune function. Because it can be stored in the body, it is important to manage intake to avoid toxicity, which can happen if taken in excessive amounts.

In contrast, the other options, such as Vitamin C and B vitamins (including B12), are classified as water-soluble vitamins. Water-soluble vitamins dissolve in water and are not stored in the body in significant amounts; they are excreted through urine when in excess, meaning they need to be consumed more regularly to maintain proper levels. Therefore, the focus on Vitamin D as a fat-soluble vitamin underscores its unique storage capability and health benefits, distinguishing it from the water-soluble counterparts.