**Core Concept**
A base of the skull fracture involving the petrous temporal bone can lead to the leakage of cerebrospinal fluid (CSF) into the surrounding tissues. This can cause various clinical signs and symptoms, including the accumulation of blood and CSF in the mastoid region.

**Why the Correct Answer is Right**
Battle's sign, characterized by ecchymosis (bruising) behind the ear, is a significant clinical indicator of a petrous temporal bone fracture. This occurs due to the leakage of CSF and blood into the mastoid region, causing inflammation and bruising. The petrous portion of the temporal bone houses the inner ear structures and is a critical area for cranial nerve VIII (vestibulocochlear nerve) transmission. The presence of Battle's sign necessitates further evaluation, including imaging studies, to confirm the diagnosis of a petrous temporal bone fracture.

**Why Each Wrong Option is Incorrect**
**Option A:** Subconjunctival hematoma is a common sign of blunt trauma but is not specifically associated with a petrous temporal bone fracture.
**Option B:** CSF rhinorrhoea is a sign of a fracture involving the anterior cranial fossa, not the petrous temporal bone. It presents as a clear nasal discharge.
**Option C:** Raccoon eyes (periorbital ecchymosis) are indicative of a fracture involving the anterior cranial fossa, often associated with a Le Fort fracture. They are not a specific sign of a petrous temporal bone fracture.

**Clinical Pearl / High-Yield Fact**
In cases of suspected petrous temporal bone fracture, it is essential to perform a thorough physical examination, including evaluation of the mastoid region for signs of bruising or swelling. Battle's sign is a critical indicator of this type of fracture, and its presence necessitates immediate further evaluation and management.

**✓ Correct Answer: D. Battle sign**