**Core Concept**
The patient's presentation suggests a traumatic injury to the head, with specific findings indicating a fracture of the temporal bone. The temporal bone houses the structures responsible for hearing and balance, and a fracture in this area can lead to complications such as hemotympanum, conductive hearing loss, and cerebrospinal fluid (CSF) leak.

**Why the Correct Answer is Right**
The patient's symptoms, including hemotympanum, a clear, watery fluid dripping from the nose (indicative of CSF leak), and conductive hearing loss, are consistent with a temporal bone fracture. The presence of a Battle's sign, an ecchymosis in the area of the left mastoid process, further supports this diagnosis. A temporal bone fracture can occur due to the force of the fall, resulting in a fracture of the petrous part of the temporal bone.

**Why Each Wrong Option is Incorrect**
**Option A:** A frontal sinus fracture would not typically present with the specific combination of symptoms seen in this patient, including hemotympanum and CSF leak.

**Option B:** A mastoid process fracture, while possible, would not typically result in a CSF leak through the nose.

**Option C:** A petrous apex fracture is a rare injury that would not account for the patient's conductive hearing loss and hemotympanum.

**Clinical Pearl / High-Yield Fact**
Temporal bone fractures are often associated with significant head trauma, and a high index of suspicion should be maintained for these injuries in patients with head trauma and specific findings such as hemotympanum and CSF leak.

**Correct Answer:** C.