Final answer:
All of proteins, lipids, and carbohydrates are digested within the small intestine. While digestion starts at different stages and parts of the digestive system, it is completed in the small intestine with the help of digestive enzymes and bile.
Step-by-step explanation:
The correct answer to the question of which nutrients are digested within the small intestine is d. all of these choices. In the small intestine, the digestive processes for proteins, lipids (or fats), and carbohydrates are completed with the aid of intestinal and pancreatic juices. Carbohydrates begin to be digested in the mouth with the enzyme amylase, proteins are partially digested in the stomach, and lipid digestion primarily takes place in the small intestine, facilitated by bile and pancreatic lipase.Even though fat digestion begins with the emulsification of lipids by bile in the small intestine, some digestion for all three nutrients starts elsewhere. For example, protein begins to be partially digested in the stomach by the enzyme pepsin, and carbohydrate digestion starts in the mouth with the enzyme salivary amylase. However, their complete digestion occurs in the small intestine.