**Core Concept**
Lysozyme is an enzyme that plays a crucial role in the innate immune system by breaking down bacterial cell walls, specifically peptidoglycans. This mechanism is essential for preventing bacterial infections and is found in various bodily secretions.

**Why the Correct Answer is Right**
The correct answer is a mucous membrane, such as the nasal or salivary mucosa. Lysozyme is secreted by mucous membranes and works by hydrolyzing the peptidoglycan layer of bacterial cell walls, ultimately leading to bacterial lysis. This process is mediated by the enzyme's ability to bind to and cleave the glycosidic bonds in peptidoglycan.

**Why Each Wrong Option is Incorrect**
**Option A:** Tears - While tears do contain some lysozyme, they are not the primary source of this enzyme.
**Option B:** Pancreatic juice - Pancreatic juice contains other digestive enzymes but not significant amounts of lysozyme.
**Option C:** Gastric juice - Gastric juice has a high pH, which inactivates lysozyme, making it an unlikely source.

**Clinical Pearl / High-Yield Fact**
Lysozyme is an important component of the innate immune system, and its activity can be enhanced by using antimicrobial peptides or other compounds that target bacterial cell walls.

**Correct Answer:** C.