**Core Concept**
The patient's presentation suggests a case of **hypovolemic shock**, likely due to internal bleeding from the head injury. This condition is characterized by decreased **blood volume**, leading to inadequate **perfusion** of vital organs.

**Why the Correct Answer is Right**
The correct answer is related to the patient's symptoms, which are consistent with **hypovolemic shock**. The low **blood pressure** (90/60 mmHg) and **tachycardia** indicate a state of decreased **circulating blood volume**. This is likely due to internal bleeding, which can occur after a head-on collision.

**Why Each Wrong Option is Incorrect**
**Option A:** Not provided, cannot be evaluated.
**Option B:** Not provided, cannot be evaluated.
**Option C:** Not provided, cannot be evaluated.
**Option D:** Not provided, cannot be evaluated.

**Clinical Pearl / High-Yield Fact**
In cases of **head injury**, it is essential to consider the possibility of **cervical spine injury** and **internal bleeding**, which can lead to **hypovolemic shock**.

**Correct Answer:** D. Hypovolemic shock.