**Core Concept**
Rigor mortis is a post-mortem process characterized by muscle stiffening and rigidity due to changes in the muscle fibers and their associated proteins. It occurs after death and is influenced by factors such as temperature, muscle type, and the presence of certain enzymes.

**Why the Correct Answer is Right**
The correct answer is related to the biochemical process that leads to muscle stiffening. During rigor mortis, calcium ions (Ca2+) are released from the sarcoplasmic reticulum, triggering the binding of actin and myosin filaments. This binding is facilitated by the enzyme parvalbumin, which sequesters magnesium ions (Mg2+) and allows calcium ions to bind to troponin and tropomyosin, ultimately leading to muscle contraction and stiffness. The correct answer simulates this process by mimicking the release of calcium ions.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the biochemical process leading to rigor mortis. While cold temperatures can slow down the process, they do not simulate the release of calcium ions.

**Option B:** This option is incorrect because it refers to a different physiological process. While epinephrine can cause muscle contraction, it does not simulate the post-mortem changes that occur during rigor mortis.

**Option C:** This option is incorrect because it does not accurately describe the biochemical process leading to rigor mortis. While certain enzymes, such as parvalbumin, are involved in the process, this option does not specifically simulate the release of calcium ions.

**Clinical Pearl / High-Yield Fact**
The rate and extent of rigor mortis can be influenced by factors such as temperature, muscle type, and the presence of certain enzymes. In forensic medicine, the study of rigor mortis can provide valuable information about the time of death and the circumstances surrounding it.

**Correct Answer: D. Cold water immersion.**