**Core Concept**
Muscular changes after death are a key aspect of forensic pathology, as they can provide valuable information about the circumstances surrounding a person's demise. The muscular changes that occur after death are influenced by various factors, including the position of the body, the presence of rigor mortis, and the breakdown of muscle tissue by enzymes.

**Why the Correct Answer is Right**
Rigor mortis is a well-known phenomenon that occurs after death, characterized by the stiffening of muscles due to the accumulation of lactic acid and the depletion of ATP. This process typically begins within 2-4 hours after death and can last for several days. However, **Option C** is likely the correct answer, as it is the only statement that is true about muscular changes after death.

**Why Each Wrong Option is Incorrect**
* **Option A:** This statement is false because the breakdown of muscle tissue by enzymes, such as proteases, is a normal process that occurs after death, but it is not the primary cause of muscular changes.
* **Option B:** This statement is false because the absence of rigor mortis is not a characteristic of muscular changes after death. In fact, rigor mortis is a hallmark of death and can provide valuable information about the timing of death.
* **Option D:** This statement is false because the relaxation of muscles is not a characteristic of muscular changes after death. In fact, muscles typically become stiff and rigid after death due to rigor mortis.

**Clinical Pearl / High-Yield Fact**
The duration of rigor mortis can provide valuable information about the timing of death. In general, rigor mortis begins to resolve within 2-4 days after death, but this can vary depending on factors such as temperature and the presence of certain medical conditions.

**Correct Answer: C. Rigor mortis is a well-known phenomenon that occurs after death, characterized by the stiffening of muscles due to the accumulation of lactic acid and the depletion of ATP.**