Critical Reasoning

Certain messenger molecules fight damage to the lungs from noxious air by telling the muscle cells encircling
the lungs' airways to contract. This partially seals off the lungs. An asthma attack occurs when the
messenger molecules are activated unnecessarily, in response to harmless things like pollen or household
dust.
Which of the following, if true, points to the most serious flaw of a plan to develop a medication that would
prevent asthma attacks by blocking receipt of any messages sent by the messenger molecules referred to
above?
(A) Researchers do not yet know how the body produces the messenger molecules that trigger asthma
attacks.
(B) Researchers do not yet know what makes one person's messenger molecules more easily activated than
another's.
(C) Such a medication would not become available for several years, because of long lead times in both
development and manufacture.
(D) Such a medication would be unable to distinguish between messages triggered by pollen and household
dust and messages triggered by noxious air.
(E) Such a medication would be a preventative only and would be unable to alleviate an asthma attack once
it had started.

Guys i marked B but OA is different.
I didn't understand the underlying logic.
Pls explain.

Thanks in Advance