Final answer:
The clinical sign of a unilateral fracture of the body of the zygoma is subconjunctival haemorrhage. This condition arises due to the close proximity of the zygoma to the orbital structures, which can lead to bleeding under the conjunctiva of the eye.
Step-by-step explanation:
The question asks for a clinical sign of a unilateral fracture of the body of the zygoma. Among the given options, the correct answer is C. subconjunctival haemorrhage. This is because the zygoma, also known as the cheekbone, is in close relation to the orbital structures; thus, trauma resulting in a zygomatic fracture often presents with subconjunctival haemorrhage. Options such as cerebrospinal rhinorrhea or otorrhea typically relate to fractures of the cranial base, not to isolated zygomatic fractures, while impaired hearing could be associated with damage to the bones of the middle ear or cochlea, which are not directly related to the zygoma.