## Core Concept
Wound classification, also known as surgical wound classification, is a system used to categorize surgical wounds based on their risk of infection. This classification helps in predicting the risk of surgical site infections (SSIs) and guides the use of prophylactic antibiotics. The classification includes four categories: clean, clean-contaminated, contaminated, and dirty/infected.

## Why the Correct Answer is Right
A Grade III or contaminated wound is one in which there is an open, fresh, accidental wound. In addition to this, operations with major breaks in sterile technique (e.g., open cardiac massage) or gross spillage from the gastrointestinal tract, or incisions in which acute, nonpurulent inflammation is encountered, including necrotic tissue without purulent drainage are classified under this category. The presence of inflammation or the entry into a viscus (organ) increases the risk of infection.

## Why Each Wrong Option is Incorrect
- **Option A:** Clean wounds are those in which the respiratory, alimentary, genital, or urinary tracts are not entered. The risk of infection is relatively low. This does not match the description of a Grade III wound.
- **Option B:** Clean-contaminated wounds involve entry into a viscus (like the respiratory, alimentary, genital, or urinary tracts) under controlled conditions and without unusual contamination. This category does not fit the Grade III criteria.
- **Option D:** A dirty or infected wound involves existing clinical infection or perforated viscera. This represents a higher risk than a Grade III wound.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the classification of wounds into clean, clean-contaminated, contaminated, and dirty/infected helps guide antibiotic prophylaxis and predict the risk of surgical site infections. For contaminated (Grade III) wounds, the infection risk is higher than clean or clean-contaminated wounds, but not as high as dirty/infected wounds.

## Correct Answer: C.