**Core Concept**
The pancreas contains two main types of cells: alpha cells and beta cells. Beta cells are responsible for the production and secretion of insulin, a hormone that regulates blood glucose levels. In addition to insulin, beta cells also secrete other hormones that play a crucial role in glucose metabolism.

**Why the Correct Answer is Right**
Insulin and glucagon are two hormones secreted by the pancreas that have opposing effects on blood glucose levels. Insulin lowers blood glucose levels by facilitating glucose uptake in cells, while glucagon raises blood glucose levels by stimulating the breakdown of glycogen and gluconeogenesis. The co-secretion of insulin and glucagon by beta cells helps to maintain glucose homeostasis. When blood glucose levels are high, beta cells secrete insulin to lower blood glucose levels. When blood glucose levels are low, beta cells secrete glucagon to raise blood glucose levels.

**Why Each Wrong Option is Incorrect**
**Option A:** Amylin is a hormone secreted by the pancreas, but it is not secreted by beta cells in the same manner as insulin and glucagon. Amylin is secreted along with insulin and helps to regulate postprandial glucose levels.

**Option B:** Somatostatin is a hormone that inhibits the secretion of other hormones, including insulin and glucagon. It is not secreted by beta cells and does not play a role in glucose homeostasis.

**Option C:** Pancreatic polypeptide is a hormone secreted by the pancreas, but it is not secreted by beta cells. It is involved in regulating pancreatic exocrine function.

**Option D:** C-peptide is a byproduct of insulin synthesis and is secreted by beta cells along with insulin. However, it is not a hormone with a distinct physiological function.

**Clinical Pearl / High-Yield Fact**
The co-secretion of insulin and glucagon by beta cells helps to maintain glucose homeostasis and prevents hypoglycemia. This is a critical concept for understanding the regulation of blood glucose levels and the pathophysiology of diabetes mellitus.

**Correct Answer: C. Glucagon**