**Core Concept**
The Glasgow Coma Scale (GCS) is a neurological scale used to assess the level of consciousness in a person after a head injury. It consists of three components: Eye Opening, Verbal Response, and Motor Response, each scored from 1 to 5. The total score ranges from 3 (indicating deep coma or death) to 15 (indicating full consciousness).

**Why the Correct Answer is Right**
A mild head injury typically corresponds to a GCS score of 14 or 15. This is because the person is fully awake and alert, with no apparent deficit in consciousness or cognitive function. The GCS score is a useful tool in assessing the severity of head injuries and guiding treatment decisions.

**Why Each Wrong Option is Incorrect**
* **Option A:** This score is typically associated with moderate head injuries, where the person may be lethargic or confused.
* **Option B:** This score is often seen in severe head injuries, where the person may be comatose or unresponsive.
* **Option C:** This score is also associated with severe head injuries, where the person may be in a deep coma or have a poor prognosis.

**Clinical Pearl / High-Yield Fact**
The GCS score is a crucial component of the initial assessment of patients with head injuries, and it helps guide the decision to perform imaging studies, such as CT scans, to evaluate for intracranial hemorrhage or other complications.

**Correct Answer: D. 15**