Final answer:
Brunner glands, also known as duodenal glands, are mucous-secreting glands found in the submucosa of the duodenum, making b. duodenum the correct answer.
Step-by-step explanation:
The Brunner glands, also known as the duodenal glands, are characteristic mucous-secreting glands found in the submucosa of the duodenum. The duodenum is the first part of the small intestine, which starts at the pyloric sphincter and ends at the jejunum. Therefore, the correct answer to the question, which asks which part of the gastrointestinal tract contains Brunner glands, is b. duodenum.
Additionally, as part of the large intestines, the cecum is the part that attaches to the appendix, villi are most associated with the small intestine, and most fat-digesting enzymes are produced by the pancreas.