Final answer:
Fat-soluble vitamins (A, D, E, and K) are primarily absorbed in the ileum of the small intestine alongside dietary fats within micelles.
Step-by-step explanation:
The absorption of fat-soluble vitamins A, D, E, and K occurs in the small intestine, specifically within the micelles that transport dietary lipids through simple diffusion. Although water and lipids are absorbed throughout the entirety of the small intestine, including the duodenum, jejunum, and ileum, it is the ileum where the absorption of certain nutrients and bile salts mainly takes place. Moreover, considering the role of the ileum in absorbing molecules like vitamin B12 and its adaptation for reclaiming bile salts, the ileum is also the primary site for the absorption of fat-soluble vitamins alongside the dietary fats.
Vitamin D can also be synthesized in the skin through exposure to sunlight. They, being fat-soluble, are stored within the body's lipid stores, which means they can accumulate to levels that could cause hypervitaminosis if consumed in excess. To facilitate their absorption, it is recommended to consume fat-soluble vitamins with some fatty foods.
Using the information provided and the overall knowledge about nutrient absorption in the small intestine, the correct answer to the question is B. ileum.