**Core Concept**
The underlying principle being tested involves the correlation of clinical manifestations such as mental retardation, recurrent seizures, and hemangioma with specific neuroimaging findings on a CT scan. This scenario suggests a **phakomatosis**, a group of disorders characterized by the presence of hamartomas in multiple organs.

**Why the Correct Answer is Right**
Given the combination of symptoms like mental retardation, seizures, and hemangioma, the most likely diagnosis is **Sturge-Weber syndrome**, a condition characterized by a congenital facial hemangioma, neurological abnormalities, and glaucoma. The CT scan would typically show **calcifications** in the brain, particularly in the occipital region, which are pathognomonic for this condition.

**Why Each Wrong Option is Incorrect**
**Option A:** This choice is incorrect because it does not correlate with the classic triad of Sturge-Weber syndrome.
**Option B:** This option is also incorrect as it does not align with the typical presentation of seizures and hemangioma.
**Option C:** Incorrect because it lacks the specific neuroimaging findings associated with the described clinical scenario.
**Option D:** This choice is incorrect as it does not match the provided clinical and radiological features.

**Clinical Pearl / High-Yield Fact**
Sturge-Weber syndrome is a key diagnosis to consider in patients with a port-wine stain (hemangioma) and neurological symptoms. The presence of **intracranial calcifications** on CT scan is a hallmark of this condition.

**Correct Answer:** D. Sturge-Weber syndrome.