**Composition of Fixer Solution**

### Core Concept
Fixer solution is a chemical used in photography to stabilize and fix the image after it has been exposed and developed. The composition of fixer solution is critical in ensuring the removal of unexposed silver halides from the photographic emulsion, preventing further development and allowing for the preservation of the image.

### Why the Correct Answer is Right
The fixer solution typically contains sodium thiosulfate (Na2S2O3) as the primary component. Sodium thiosulfate acts as a reducing agent, converting the silver halides into silver thiosulfate complexes, which are soluble in water. This reaction is crucial in removing the unexposed silver halides from the emulsion, thereby stabilizing the image. The presence of sodium thiosulfate also helps to prevent further development of the image by removing the remaining silver halides.

### Why Each Wrong Option is Incorrect
**Option A:** Ammonium thiosulfate is not typically used as the primary component in fixer solution, although it can be used as an alternative to sodium thiosulfate.
**Option B:** Sodium sulfite is not a primary component of fixer solution, although it may be used in some photographic processes as a preservative.
**Option C:** Glutathione is not a component of fixer solution and is not related to the photographic process.

### Clinical Pearl / High-Yield Fact
It's essential to note that the composition of fixer solution can vary depending on the type of photographic process being used. However, sodium thiosulfate remains the primary component in most fixer solutions.

### Correct Answer: C. Glutathione is not a component of fixer solution and is not related to the photographic process.