**Core Concept**
Gastrointestinal hormones are signaling molecules produced by the gastrointestinal tract that regulate various physiological processes, including digestion, motility, and secretion. These hormones play a crucial role in maintaining homeostasis and ensuring proper nutrient absorption.

**Why the Correct Answer is Right**
Chymotrypsin is a digestive enzyme produced by the pancreas, specifically by acinar cells. Unlike gastrointestinal hormones, chymotrypsin is a proteolytic enzyme that breaks down proteins into smaller peptides. It is not a hormone, but rather an enzyme that plays a vital role in protein digestion in the small intestine. Chymotrypsin is activated in the small intestine, where it helps to hydrolyze proteins into amino acids for absorption. The other options, CCK-PZ (cholecystokinin-pancreozymin), GIP (glucose-dependent insulinotropic peptide), and motilin, are all gastrointestinal hormones that regulate various physiological processes in the gastrointestinal tract.

**Why Each Wrong Option is Incorrect**
**Option A:** CCK-PZ is a gastrointestinal hormone released by the duodenum in response to the presence of fatty acids and amino acids. It stimulates the release of digestive enzymes from the pancreas and bile from the gallbladder.
**Option B:** GIP is a gastrointestinal hormone released by the duodenum in response to the presence of glucose. It stimulates the release of insulin from the pancreas and regulates glucose metabolism.
**Option D:** Motilin is a gastrointestinal hormone released by the duodenum in response to the presence of nutrients. It stimulates the migration of the interdigestive migrating myoelectric complex (IMMC) and regulates gastrointestinal motility.

**Clinical Pearl / High-Yield Fact**
Gastrointestinal hormones play a crucial role in regulating digestive processes, and their dysregulation can lead to various gastrointestinal disorders, such as diarrhea, constipation, and malabsorption. Understanding the functions and interactions of these hormones is essential for diagnosing and managing gastrointestinal diseases.

**✓ Correct Answer: C. Chymotrypsin**