Vitamin A was the first fat-soluble vitamin, comprises of the preformed retinoids, plus the precursor forms, the provitamin A carotenoids. Preformed retinoids is a collective term for retinol, retinal, and retinoic acid, all of which are biologically active. The provitamin A carotenoids include beta-carotene and others, which are converted to retinoids with varying degrees of efficiency. Retinoids are sensitive to heat, light, and oxidation by air.
Retinoids are converted to retinol in the intestines and transported with dietary fat to the liver, where it is stored. A special transport protein, retinol binding protein (RBP), transports vitamin A from the liver to other tissues. Carotenoids are absorbed intact at a much lower absorption rate than retinol. Of all the carotenoids, beta-carotene has the highest potential vitamin-A activity. The active forms of vitamin A have three basic functions: vision, growth and development of tissues, and immunity
So, the correct answer is 'Intestinal tract'