**Core Concept**
The Glasgow Coma Score (GCS) is a neurological scale used to assess the conscious level of a patient. It is a widely used tool in the assessment and management of head injuries and other conditions that may affect the level of consciousness.

**Why the Correct Answer is Right**
The GCS is a 15-point scale that evaluates three aspects of a patient's consciousness: eye opening, verbal response, and motor response. The total GCS score ranges from 3 to 15, with higher scores indicating better consciousness. The minimum score of 3 is obtained when a patient is unresponsive and has no eye opening, verbal response, or motor response. Conversely, the maximum score of 15 is achieved when a patient is fully awake and has a normal eye opening, verbal response, and motor response.

**Why Each Wrong Option is Incorrect**
* **Option B:** This option incorrectly states that the minimum GCS score is 0. However, the GCS scale starts from 3, not 0.
* **Option C:** This option incorrectly states that the maximum GCS score is 13. The correct maximum score is 15.
* **Option D:** This option incorrectly states that the minimum GCS score is 3 but the maximum score is 18. The correct maximum score is 15, not 18.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that the GCS is a valuable tool in assessing the severity of head injuries and guiding treatment. A low GCS score is associated with a higher risk of poor outcomes, including death and neurological disability.

**✓ Correct Answer: A. Minimum = 3, Maximum = 15**