Which of the following is considered a fat-soluble vitamin?

Vitamin K is categorized as a fat-soluble vitamin, which means it is absorbed along with fats in the diet and can be stored in the body's fatty tissues and liver. Fat-soluble vitamins, including vitamins A, D, E, and K, have specific roles in the body, such as maintaining bone health, supporting immune function, and aiding in blood clotting processes.

In contrast, water-soluble vitamins, such as vitamin C and the B-vitamins (including vitamin B12), do not have the same storage capabilities in the body and are typically excreted through urine. This distinction is crucial in understanding how different vitamins function and are utilized by the body, as it informs dietary recommendations and the management of deficiencies. Therefore, the correct answer points to vitamin K being a vital fat-soluble vitamin essential for various physiological functions.