Final answer:
Vitamin D is the vitamin that is absorbed through the skin, primarily when the skin is exposed to sunlight or through topical application. Other fat-soluble vitamins such as A, E, and K are absorbed through the intestinal tract. The correct answer is (b).
Step-by-step explanation:
Vitamin D Synthesis: Vitamin D is unique among the listed vitamins as it can be synthesized in the skin when exposed to sunlight. Ultraviolet B (UVB) radiation from the sun triggers the conversion of 7-dehydrocholesterol in the skin to previtamin D₃.
Sun Exposure: When the skin is exposed to sunlight, specifically UVB rays, it catalyzes the synthesis of vitamin D₃ in the skin.
Activation: The provitamin D₃ undergoes further processes in the liver and kidneys to become active vitamin D (calcitriol), which is essential for the regulation of calcium and phosphate metabolism.
Other Vitamins: While vitamins A and K are essential for various physiological functions, they are not synthesized in the skin through exposure to sunlight. Vitamin A is typically obtained through dietary sources, and vitamin K is synthesized by intestinal bacteria and obtained through dietary intake.
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Among the listed options, only vitamin D is synthesized in the skin through exposure to sunlight.