**Core Concept**
The question is related to the post-mortem findings in a case of carbon monoxide (CO) poisoning, which involves the binding of CO to hemoglobin in the blood. This binding results in the formation of carboxyhemoglobin, leading to tissue hypoxia. The post-mortem staining is a result of this process.

**Why the Correct Answer is Right**
In CO poisoning, the carboxyhemoglobin gives the blood a characteristic cherry-red color. This coloration is due to the binding of CO to the hemoglobin molecule, which alters its oxygen-carrying capacity and changes its color. The cherry-red discoloration can be seen in the skin, muscles, and internal organs during autopsy.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not describe the characteristic color change associated with CO poisoning.
**Option B:** This option is also incorrect as it does not accurately represent the post-mortem staining seen in CO poisoning.
**Option C:** This option is incorrect because it is not related to the specific color change caused by carboxyhemoglobin formation.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the cherry-red coloration in CO poisoning can be masked by decomposition or other factors, making diagnosis challenging. It is essential to consider the clinical history and laboratory findings, such as carboxyhemoglobin levels, to confirm the diagnosis.

**Correct Answer:** D. Cherry red discoloration.