What does the colon primarily absorb?

The colon is primarily responsible for the absorption of water, salts, and certain vitamins, including vitamin K and some B vitamins like thiamin and riboflavin. The primary function of the colon, also known as the large intestine, is to reabsorb not just water and electrolytes but also to serve as a site for the fermentation of undigested materials by gut bacteria, which can yield vitamins. Vitamin K, for instance, is produced by intestinal flora and is absorbed in the colon.

While amino acids and fatty acids are absorbed primarily in the small intestine, the colon does play a role in the absorption of certain electrolytes. However, the focus of what the colon absorbs aligns best with the absorption of water, salts, and specific vitamins, making this answer the most accurate choice.