Final answer:
The small intestine is comprised of the duodenum, jejunum, and ileum. The duodenum is the first and shortest section, followed by the jejunum, which is where most nutrient absorption occurs, and finally the ileum, the longest part that connects to the large intestine.
Step-by-step explanation:
The anatomy of the small intestine includes three major sections, which are the duodenum, jejunum, and ileum. The correct order from the stomach to the large intestine is duodenum, jejunum, and ileum, making option (a) the correct sequence. The duodenum is the first part and also the shortest segment where most chemical digestion takes place. Following the duodenum is the jejunum, around 0.9 meters (3 feet) long, where most nutrients are absorbed. Lastly, the ileum is the longest section, measuring about 1.8 meters (6 feet) in length with a thicker wall, more vascular and developed mucosal folds than the jejunum, and it connects to the large intestine at the ileocecal valve.