**Core Concept**
Subacute subdural hematoma is a type of traumatic brain injury that occurs after a head trauma, typically presenting with symptoms of irritability and altered sensorium due to gradual increase in intracranial pressure.

**Why the Correct Answer is Right**
The correct answer is subacute subdural hematoma because it occurs between 3-14 days after the initial injury, causing a gradual increase in intracranial pressure, leading to symptoms such as irritability, altered sensorium, and eventually, signs of transtentorial herniation. This type of hematoma is often associated with minor head trauma and can be challenging to diagnose due to its non-specific presentation.

**Why Each Wrong Option is Incorrect**
* **Option A:** Epidural hematoma is typically associated with a more acute presentation, often with a lucid interval, and is usually caused by a more severe head trauma.
* **Option B:** Cerebral edema can cause altered sensorium and irritability but is not a direct consequence of a head trauma and would not be the most common cause in this scenario.
* **Option D:** Contusion is a type of traumatic brain injury, but it would not typically present with features of irritability and altered sensorium 4 weeks after the initial injury.

**Clinical Pearl / High-Yield Fact**
A key clinical feature of subacute subdural hematoma is the gradual onset of symptoms, which can make diagnosis challenging. Always consider this diagnosis in patients with a history of head trauma and non-specific symptoms.

**Correct Answer: C. Subacute subdural hematoma.**