**Core Concept**
Cadaveric spasm, also known as instantaneous rigor, is a rare phenomenon where the muscles of the deceased individual contract and maintain their contraction for an extended period, often for hours or even days, after death. This phenomenon is distinct from the more common rigor mortis, which occurs due to the loss of ATP in muscles.

**Why the Correct Answer is Right**
Cadaveric spasm is thought to occur due to the sudden release of neurotransmitters, such as acetylcholine, at the neuromuscular junction, which causes the muscles to contract and become fixed in that position. This phenomenon is often observed in cases of violent death or in situations where the individual experiences a severe, intense stimulus, such as strychnine poisoning. The strychnine toxin blocks the inhibitory effects of glycine in the spinal cord, leading to an uncontrolled release of excitatory neurotransmitters and resulting in a sudden, violent contraction of the muscles.

**Why Each Wrong Option is Incorrect**
**Option A:** Cadaveric spasm is not a result of rigor mortis, which occurs due to the loss of ATP in muscles and is a more common phenomenon.
**Option B:** Cadaveric spasm is not a result of the post-mortem changes in the body, but rather a consequence of the specific circumstances surrounding the death.
**Option C:** Cadaveric spasm is not a result of the decomposition of the body, but rather a result of the sudden release of neurotransmitters at the neuromuscular junction.

**Clinical Pearl / High-Yield Fact**
It is essential to note that cadaveric spasm is a rare phenomenon and should not be confused with rigor mortis, which is a more common post-mortem change. The presence of cadaveric spasm can provide valuable information to investigators and can aid in the reconstruction of the events surrounding the death.

**Correct Answer:** C.