**Core Concept**
The patient's symptoms suggest a **cranial nerve VII (Facial Nerve)** injury, which controls the muscles of facial expression, including eye closure and salivation. The **facial nerve** has several branches that innervate the face, and damage to this nerve can result in weakness or paralysis of these muscles.

**Why the Correct Answer is Right**
The inability to close the left eye and drooling of saliva from the left angle of the mouth are classic signs of **facial nerve palsy**, which can occur after a head injury. The **facial nerve** controls the orbicularis oculi muscle, responsible for eye closure, and also has a branch that innervates the submandibular gland, affecting salivation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the symptoms do not suggest a **cranial nerve III (Oculomotor Nerve)** injury, which would affect eye movement.
**Option B:** This option is incorrect because the symptoms do not suggest a **cranial nerve V (Trigeminal Nerve)** injury, which would affect facial sensation.
**Option C:** This option is incorrect because the symptoms do not suggest a **cranial nerve XII (Hypoglossal Nerve)** injury, which would affect tongue movement.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **cranial nerve VII (Facial Nerve)** injury can result in **ipsilateral** (same side) facial weakness, which is a critical distinction in diagnosing and localizing neurologic lesions.

**Correct Answer:** D. Facial Nerve Injury