**Core Concept**
The estimation of the post-mortem interval (PMI) in vitreous humor is a crucial aspect of forensic pathology, used to determine the time since death. The vitreous humor is the clear gel-like substance filling the center of the eyeball, which can provide valuable information about the deceased's metabolic state and hydration status.

**Why the Correct Answer is Right**
The correct answer is based on the fact that the concentration of potassium ions (K+) in the vitreous humor increases over time after death, making it a reliable indicator of the post-mortem interval. This increase in potassium is due to the breakdown of cellular components and the release of intracellular potassium into the vitreous humor. The rate of potassium increase is relatively consistent, allowing for an estimate of the time since death.

**Why Each Wrong Option is Incorrect**
* **Option A:** Lactic acid is not typically measured in vitreous humor for estimating the post-mortem interval.
* **Option B:** Chloride levels in the vitreous humor do not correlate well with the post-mortem interval.
* **Option C:** Glucose levels in the vitreous humor are not a reliable indicator of the post-mortem interval, as glucose can be influenced by various factors such as the deceased's diet and diabetes status.

**Clinical Pearl / High-Yield Fact**
The vitreous humor is an excellent medium for estimating the post-mortem interval due to its relatively stable composition and the consistent rate of potassium increase after death. This makes it a valuable tool for forensic pathologists in determining the time since death.

**Correct Answer:** C. Potassium