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: Ophthalmology
Which of the following is true regarding Electrocochleography 
Select and explain. 
A. It measures middle ear latency, B. Outer hair cells are mainly responsible for cochlear microphonics and summation potentia, C. Summation potential is a compound of synchronous auditory nerve potentials, D. Total action potentials represents the endocochlear receptor potential to an external auditory stimulus
B: Outer hair cells are mainly responsible for cochlear microphonics and summation potentia
Answer: B: Outer hair cells are mainly responsible for cochlear microphonics and summation potentia 
Explanation: Ans. b. Outer hair cells are mainly responsible for cochlear microphonics and summation potential Outer hair cells are mainly responsible for cochlear microphonics and summation potential. Electrocochleography: ECoG is inner ear (not the middle ear) potential measurement Action potential (AP) is a compound of synchronous auditory nerve potentials AP represents neural potential Electrocochleography Electrocochleography (ECoG) measures the electrical potential arising in the cochlea and the eights cranial nerve in response to auditory stimuli within first few milliseconds Constituents of an ECoG Cochlear microphonic (CM) Summating potential (SP) Compound Action Potential (AP) Generated predominantly the outer hair cells of theorgan of Coi. Generated predominantlyby the outer hair cells ofthe organ of Coi Represents the summed response of thesynchronous firing of several thousandsauditory nerve fibers Reflects predominantlybasal-end cochlear activitywhen recorded from theround window and moreremote sites. ECoG of patients withMeniere's disease/endolymphatic hydropsoften display enlargedSPs Most popular application of the AP involves measurement of its magnitude in comparisonto that of SP in patients suspected of havingMeniere's disease (endolymphatic Hydrops Enlarged SP/AP amplitude ratio to click stimuli