First part of the small intestine.

First part of the small intestine.

• A. Ileum
• B. Pericardium
• C. Duodenum
• D. Phlebitis

Answer: (C)

The main idea is identifying the first section of the small intestine. The duodenum is that opening segment—right after the stomach—where chyme mixes with bile and pancreatic juice to start digestion and neutralize stomach acid. It’s the initial part of the small intestine, about 25–30 cm long, setting the stage for nutrient absorption that occurs later in the jejunum and ileum. The ileum is a later portion of the small intestine, while the pericardium is the heart’s enclosing membrane, and phlebitis is inflammation of a vein — both unrelated to the digestive tract.

The main idea is identifying the first section of the small intestine. The duodenum is that opening segment—right after the stomach—where chyme mixes with bile and pancreatic juice to start digestion and neutralize stomach acid. It’s the initial part of the small intestine, about 25–30 cm long, setting the stage for nutrient absorption that occurs later in the jejunum and ileum. The ileum is a later portion of the small intestine, while the pericardium is the heart’s enclosing membrane, and phlebitis is inflammation of a vein — both unrelated to the digestive tract.