**Core Concept**
Acute stroke is a cerebrovascular event that leads to rapid loss of brain function. Common complications arise due to the sudden interruption of blood flow to the brain, resulting in tissue damage and increased intracranial pressure.

**Why the Correct Answer is Right**
The most common complication of acute stroke is cerebral edema, which occurs due to the breakdown of the blood-brain barrier and increased vascular permeability. This leads to the accumulation of fluid in the brain parenchyma, causing increased intracranial pressure and potentially life-threatening complications. The pathophysiology involves the activation of various inflammatory pathways, release of pro-inflammatory cytokines, and disruption of tight junctions between endothelial cells.

**Why Each Wrong Option is Incorrect**
**Option A:** Hypertension is a risk factor for stroke, but it is not a common complication of acute stroke.
**Option B:** Seizure is a potential complication of stroke, but it is not as common as cerebral edema.
**Option C:** Infection is a potential complication of stroke, particularly in the context of brain abscess formation, but it is not as common as cerebral edema.

**Clinical Pearl / High-Yield Fact**
In patients with acute stroke, early recognition and management of cerebral edema are critical to prevent further brain damage and improve outcomes. This involves monitoring intracranial pressure, administering corticosteroids, and using other supportive measures to reduce intracranial pressure.

**Correct Answer:** C. Cerebral edema.