**Core Concept**
The intercalated ducts are a critical component of the exocrine pancreas, playing a pivotal role in the regulation of pancreatic secretion. They are responsible for the final modification and secretion of pancreatic juice into the duodenum.

**Why the Correct Answer is Right**
The primary functions of intercalated ducts include the reabsorption of water and electrolytes, modification of the pH of pancreatic juice through the secretion of bicarbonate, and the secretion of digestive enzymes. The intercalated ducts also facilitate the exchange of ions and water with the surrounding connective tissue, thereby regulating the concentration of pancreatic juice.

**Why Each Wrong Option is Incorrect**
**Option A:** This option might be a plausible function of intercalated ducts, but it is not the correct answer. Intercalated ducts do play a role in the secretion of digestive enzymes, but this is not their primary function.
**Option B:** This option is incorrect because the regulation of pancreatic secretion is a function of the acinar cells, not the intercalated ducts.
**Option C:** This option is incorrect because the secretion of mucus is a function of the goblet cells, not the intercalated ducts.

**Clinical Pearl / High-Yield Fact**
The intercalated ducts are a common site for the development of pancreatic calculi, particularly in patients with chronic pancreatitis.

**Correct Answer:** D.