**Core Concept**
PM staining, or postmortem lividity, refers to the gravitational settling of blood in dependent parts of the body after death. It is a hallmark of postmortem changes and is clinically identified by the presence of purplish discoloration in areas where blood pools due to gravity.

**Why the Correct Answer is Right**
Livor mortis (also known as cadaveric lividity or livor mois) is the correct term for PM staining in dependent parts of the body. "Suggilation" is an outdated term used in historical texts to describe livor mortis, though it is not standard. "Algor mortis" refers to the cooling of the body after death, not discoloration. Thus, "Algor mois" is a misnomer and does not describe PM staining — it describes body temperature decline, not blood pooling.

**Why Each Wrong Option is Incorrect**
Option A: Cadaveric lividity is a synonym for livor mortis and correctly describes PM staining.
Option B: Suggilation is an archaic term used in some forensic texts to denote livor mortis, though rare, it is considered a synonym.
Option C: Livor mois is the standard term for postmortem lividity and is directly synonymous with PM staining.
Option D: Algor mois is incorrect because it refers to the postmortem cooling of the body (algor mortis), not blood pooling or discoloration.

**Clinical Pearl / High-Yield Fact**
Remember: **Livor mortis = discoloration**, **Algor mortis = cooling**. Confusing these two is a common exam trap — always distinguish between discoloration and temperature changes in postmortem changes.

✓ Correct Answer: D. Algor mois