**Core Concept**
The digestion of disaccharides involves the breakdown of two simpler sugar molecules into their constituent monosaccharides. This process is primarily facilitated by enzymes that are secreted by the pancreas and then released into the small intestine.

**Why the Correct Answer is Right**
The correct answer, C. Small intestine, is due to the presence of specific enzymes such as sucrase, maltase, and lactase, which are produced by the pancreas and then released into the small intestine. These enzymes catalyze the hydrolysis of disaccharides like sucrose, maltose, and lactose into their constituent monosaccharides, including glucose and fructose. The small intestine provides an ideal environment for this process to occur, with a large surface area and a suitable pH range for enzyme activity.

**Why Each Wrong Option is Incorrect**
* **Option A:** The mouth is primarily responsible for mechanical breakdown of food through chewing and the initiation of digestion through salivary amylase, but it does not play a significant role in the digestion of disaccharides.
* **Option B:** The stomach secretes gastric amylase, which breaks down starches into shorter chains of glucose, but it does not have the necessary enzymes to digest disaccharides.
* **Option D:** The large intestine is mainly involved in water absorption and the fermentation of undigested carbohydrates by colonic bacteria, but it does not have the enzymes necessary for the digestion of disaccharides.

**Clinical Pearl / High-Yield Fact**
The digestion of disaccharides is a crucial step in carbohydrate metabolism, and deficiencies in the enzymes responsible for this process can lead to conditions such as lactose intolerance, sucrose intolerance, and glucose-galactose malabsorption.

**✓ Correct Answer: C. Small intestine**