**Core Concept**
Bulk-forming laxatives work by increasing the bulk of the stool through the absorption of water, making the stool softer and easier to pass. They contain non-digestible carbohydrates such as psyllium, methylcellulose, or polycarbophil that form a gel-like substance in the colon, increasing the stool's bulk and promoting bowel movements.

**Why the Correct Answer is Right**
Bulk-forming laxatives like psyllium (Option C) and polycarbophil work by absorbing water and forming a gel-like substance in the colon, increasing the stool's bulk and promoting bowel movements. This process helps to soften the stool and make it easier to pass. Psyllium, in particular, is a type of soluble fiber that is commonly used in bulk-forming laxatives.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not a bulk-forming laxative, but rather a type of stimulant laxative that works by increasing the motility of the intestines to stimulate bowel movements.
**Option B:** This option is not a bulk-forming laxative, but rather a type of osmotic laxative that works by drawing water into the colon to soften the stool and promote bowel movements.
**Option D:** This option is not a bulk-forming laxative, but rather a type of stool softener that works by reducing the surface tension of the stool to make it softer and easier to pass.

**Clinical Pearl / High-Yield Fact**
Bulk-forming laxatives can be effective in promoting regular bowel movements, but they may not be suitable for patients with swallowing difficulties or those who have a narrow esophagus. It's essential to recommend bulk-forming laxatives with a glass of water and to instruct patients to take them with a full glass of water to prevent esophageal obstruction.

**Correct Answer:** C. Psyllium