This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: ENT
Facial nerve palsy at sternomastoid canal can cause- 
Select and explain. 
A. Loss of corneal reflex at side of lesion, B. Loss of taste sensation anterior 2/3 of ipsilateral tongue, C. Loss of lacrimation at side of lesion, D. Hyperacusis
A: Loss of corneal reflex at side of lesion
Answer: A: Loss of corneal reflex at side of lesion 
Explanation: Below stylomastoid foramen, facial nerve gives following branches: - Posterior auricular branch, muscular branches (stylohyoid & posterior belly of digastric) and terminal (peripheral) branches.
Lesion at sternomastoid foramen : -

i)    Will spare

Greater superficial petrosal nerve → Lacrimation present.
Nerve to stapedius → Normal stapedial reflex and no hyperacusis.
Chorda tympani → Normal salivation and a taste sensation in anterior 2/3 of the tongue.

ii) Will involve

Terminal (peripheral) branches → Paralysis of muscles of facial expression. Corneal reflex will also be lost because efferent fibres of corneal reflex are derived from peripheral branches of the facial nerve.