Dermatologists are trained to distinguish an irritation, which results from prolonged exposure to the offending substance, from a true allergic reaction, which manifests itself immediately upon contact with the allergen.
A.
an irritation, which results from prolonged exposure to the offending substance, from a true allergic reaction, which manifests itself immediately upon contact with the allergen CorrectB. an irritation, resulting from prolonged exposure to the offending substance,
and a true allergic reaction, manifesting itself immediately upon contact with the allergen
Incorrect C.
between an irritation, which results from prolonged exposure to the offending substance,
or a true allergic reaction, which manifests itself immediately upon contact with the allergen
IncorrectD.
between an irritation, resulting from prolonged exposure to the offending substance,
from a true allergic reaction, manifesting itself immediately upon contact with the allergen
IncorrectE. a true allergic reaction, which manifests itself immediately upon contact with the allergen,
and an irritation, which results from prolonged exposure to the offending substance
Incorrectcorrect idioms - .........distinguish X from Y
.........between X and Y
B, C, D & E violates these two idioms; so Answer A