Here is the text of the question:

A new medical procedure replaces all three of the tiny bones in the inner ear with a single piece of ultra-thin fiberglass. The procedure has been found to greatly improve hearing in people who have experienced damage to these bones, though it is useless to people whose hearing loss stems from a neurological malfunction. This procedure will benefit a relatively small percentage of the hearing-impaired population

Which of the following can be concluded from the argument above?

A)It is possible to hear without the use of the three tiny bones in the inner ear.
B)Most hearing loss is due to neurological malfunctioning.
C)More people have impaired hearing because of neurological damage than because of damage to the tiny bones of the inner ear.
D)Hearing loss due to neurological damage is more severe than hearing loss due to damage to the tiny bones in the inner ear.
E)The use of fiberglass cannot help people who have lost hearing due to neurological damage.

Notice that the question stem says "Which of the following can be concluded from the argument above?"

This is an inference question. Which means that you are looking for the answer choice that must be true.

If we look at choices B and C that you favored, you can see that these are not "must be true."

Choice B "Most hearing loss is due to neurological malfunctioning." There is no quantification of causes of hearing loss in the stimulus. It may be true that neurological malfunctioning is the top cause, but then it may also be that the biggest cause of hearing loss is damage from loud noise. The point is that this is not "must be true."

Choice C "More people have impaired hearing because of neurological damage than because of damage to the tiny bones of the inner ear." is wrong for exactly the same reason. There is no indication of the number of people suffering do to the various causes.

Choice A, on the other hand, MUST BE TRUE, "A)It is possible to hear without the use of the three tiny bones in the inner ear."

We know this because the stimulus says, "A new medical procedure replaces all three of the tiny bones in the inner ear with a single piece of ultra-thin fiberglass. The procedure has been found to greatly improve hearing in people who have experienced damage to these bones" If replacing the bones with fiberglass works and people can hear after the surgery it must mean that the 3 tiny bones are not 100% necessary for hearing.

So you see approaching this question as an inference really helps point directly to choice A as the correct answer.

Thanks David, for the wonderful explanation. I too reached at (A), though my reasoning was to break passage into parts: The passage starts with an introduction to "A new medical procedure replaces all three of the tiny bones in the inner ear with a single piece of ultra-thin fiberglass". The middle part elaborates the success and failure stats of the "new medical procedure". The conclusion: expected to announce some final stand about the new invention.
Choice E was an eyecatcher but E merely repeats a sentence from the passage, so that can't be the conclusion. Choice A only fits our expectation.
Is that reasoning okay? Or I just arrived at the right place with a wrong map?

~Binit.