Okay, let's tackle this question. The question is about a "blow out" fracture of the zygomatic arch and what it causes. First, I need to recall what a blow out fracture is. From what I remember, blow out fractures typically occur in the orbital floor, not the zygomatic arch. Wait, the zygomatic arch is part of the zygomatic bone, which forms the cheekbone. A fracture here might be different from a blow out fracture.

Blow out fractures usually happen when there's a direct blow to the orbit, causing the thin orbital floor to fracture. This can lead to entrapment of the inferior rectus muscle, resulting in diplopia, especially on upward gaze. But the question is about the zygomatic arch. So maybe the options are about different complications?

Wait, the zygomatic arch is part of the facial skeleton. Fractures here can affect the masticatory muscles, like the masseter and temporalis, which attach to the zygomatic arch. If the arch is fractured, these muscles might not function properly, leading to trismus (difficulty opening the mouth). Also, there's the possibility of sensory issues since the zygomatic nerve runs through the zygomatic arch.

Another thing to consider is the connection between the zygomatic bone and the maxilla. A fracture here could lead to malocclusion or facial asymmetry. But the question is specifically about a "blow out" fracture of the zygomatic arch. Wait, maybe there's confusion between blow out fracture and other types. A blow out fracture is a type of orbital fracture, while a zygomatic arch fracture is a separate entity. The options might be mixing up these concepts.

Let me check the possible options. The user hasn't provided them, but the correct answer is supposed to be explained. Let's assume the options are about complications like diplopia, trismus, sensory loss, or malocclusion. The correct answer would be trismus due to disruption of the masseter and temporalis insertion points. The other options would be incorrect because they relate to orbital floor fractures or other structures.

So, the core concept is understanding the anatomy and complications of zygomatic arch fractures versus blow out orbital fractures. The key is distinguishing between the two and knowing the specific muscles and nerves involved in each.

**Core Concept**
A **blow out fracture** of the **zygomatic arch** involves the lateral wall and floor of the orbit, often due to direct trauma. It disrupts the attachment of masticatory muscles (masseter, temporalis) and can damage the **zygomatic nerve** (a branch of the maxillary nerve), leading to sensory deficits. This differs from orbital blow-out fractures, which affect the orbital floor.

**Why the Correct Answer is Right**
The zygomatic arch fracture severs the **masseter** and **temporalis** muscles' attachment points, causing **trismus** (inability to open the mouth fully). Additionally, the **zygomatic nerve** (serving the cheek and lateral face) may be injured, causing **facial numbness**. The fracture also disrupts the **zygomaticomaxillary complex**, potentially leading to **facial asymmetry** or **diplopia** if the medial orbital wall is involved.

**Why Each Wrong

✓ Correct Answer: B. Diplopia