**Core Concept**
Papilledema is the swelling of the optic disc due to increased intracranial pressure (ICP). This condition results from the transmission of elevated ICP to the optic nerve head, causing various signs and symptoms.

**Why the Correct Answer is Right**
The correct answer, "Prominent optic disc margins," is not seen in papilledema. This is because papilledema typically presents with a blurring of the optic disc margins, making them less prominent. In contrast, conditions like optic neuritis or optic atrophy may cause prominent optic disc margins. The blurring of the optic disc margins in papilledema is due to the edema of the nerve fiber layer, which obscures the normal disc margins.

**Why Each Wrong Option is Incorrect**
* **Option A:** Marked venous engorgement is indeed seen in papilledema. Increased ICP leads to venous congestion and engorgement of the superficial retinal veins, which is a characteristic feature of papilledema.
* **Option B:** Elevation of the optic disc is a common finding in papilledema. As the optic disc swells, it becomes elevated above the surrounding retina, making it more visible.
* **Option C:** Cotton wool spots are also seen in papilledema. These are small, fluffy white patches that represent areas of ischemic damage to the retina.

**Clinical Pearl / High-Yield Fact**
In papilledema, the optic disc may appear swollen, congested, and edematous, with loss of the normal cup-disc ratio. The presence of cotton wool spots, flame-shaped hemorrhages, and retinal vessel engorgement can also support the diagnosis.

**✓ Correct Answer:** D. Prominent optic disc margins