**Core Concept**
The patient's symptoms are consistent with a sudden onset of increased intracranial pressure and irritation of the meninges, a protective membrane covering the brain and spinal cord. This condition is often associated with bleeding into the space surrounding the brain, known as the subarachnoid space.

**Why the Correct Answer is Right**
The symptoms of sudden onset severe headache (often described as "thunderclap headache") and vomiting, combined with marked neck rigidity and the absence of focal neurological deficits, are highly suggestive of a subarachnoid hemorrhage (SAH). This is because SAH typically results from the rupture of an aneurysm or other vascular anomaly in the brain, leading to bleeding into the subarachnoid space. The irritation of the meninges by blood and the subsequent increase in intracranial pressure cause the symptoms observed in this patient.

**Why Each Wrong Option is Incorrect**
**Option A:** Intracerebral parenchymal hemorrhage typically presents with focal neurological deficits due to the location of the hemorrhage within the brain parenchyma.

**Option B:** Ischemic stroke typically presents with focal neurological deficits due to the lack of blood flow to a specific area of the brain.

**Option C:** Meningitis, an infection of the meninges, may present with similar symptoms, but it is less likely to cause sudden onset severe headache and vomiting without other systemic symptoms.

**Clinical Pearl / High-Yield Fact**
The "thunderclap headache" is a classic description of the headache associated with subarachnoid hemorrhage, and it is often described as the worst headache of a patient's life.

**Correct Answer:**
✓ Correct Answer: D. Subarachnoid hemorrhage