**Core Concept**
Non-contrast computed tomography (CT) scan is the primary imaging modality used for the evaluation of acute head injuries. This is because CT scans provide rapid and accurate assessments of intracranial hemorrhage, skull fractures, and other potential complications of head trauma.

**Why the Correct Answer is Right**
The non-contrast CT scan is preferred in the acute setting due to its high sensitivity for detecting acute hemorrhage, which is a critical finding in the assessment of head trauma. The scan takes only a few minutes to perform and does not require the use of contrast agents, making it ideal for patients who may be unstable or have a history of allergies. The CT scan can also detect other complications such as skull fractures, epidural hematomas, and subarachnoid hemorrhages.

**Why Each Wrong Option is Incorrect**
**Option A:** Magnetic Resonance Imaging (MRI) is not typically used in the acute evaluation of head trauma due to its longer scan time and the potential for artifacts from metal fragments or clips.
**Option B:** Contrast-enhanced CT scans are not necessary in the acute setting and may even interfere with the evaluation of hemorrhage.
**Option C:** Plain radiographs of the skull may be used to detect skull fractures but are not sufficient for the comprehensive evaluation of acute head injuries.

**Clinical Pearl / High-Yield Fact**
In the evaluation of acute head injuries, it is essential to remember that non-contrast CT scans should be performed immediately, even if the patient is stabilized or appears clinically well, as delayed diagnosis of hemorrhage can lead to catastrophic outcomes.

**Correct Answer: A. Non-contrast CT scan of the head.**