What is the main function of the small intestine?

The main function of the small intestine is to perform the majority of nutrient absorption and chemical digestion. This part of the digestive system plays a crucial role after food has been processed in the stomach. The small intestine is divided into three segments: the duodenum, jejunum, and ileum, each contributing to the breakdown of food and the absorption of nutrients.

During digestion, enzymes from the pancreas and bile from the liver enter the small intestine, aiding in the breakdown of carbohydrates, proteins, and fats. The walls of the small intestine are lined with villi and microvilli, which significantly increase the surface area for absorption, allowing nutrients such as amino acids, fatty acids, vitamins, and minerals to enter the bloodstream efficiently.

While the other functions mentioned, such as the absorption of water or the storage of bile, are important for the digestive system, they do not primarily relate to the main role of the small intestine. The large intestine is primarily responsible for water absorption, bile is stored in the gallbladder, and waste transport is part of the excretory processes that involve other organs. Therefore, option B accurately represents the critical functions of the small intestine in the digestive process.