Q:
Sulfur dioxide, a major contributor to acid rain, is an especially serious pollutant because it diminishes the respiratory system’s ability to deal with all other pollutants.

(A) an especially serious pollutant because it diminishes the respiratory system’s ability to deal
(B) an especially serious pollutant because of diminishing the respiratory system’s capability of dealing
(C) an especially serious pollutant because it diminishes the capability of the respiratory system in dealing
(D) a specially serious pollutant because it diminishes the capability of the respiratory system to deal
(E) a specially serious pollutant because of diminishing the respiratory system’s ability to deal

I chose D, but the posted answer was A.
Isn't it better not to use 'possessive noun' expression with " 's " to mention noun which is not a human? And rather, isn't it better to use 'N of N' expression?

In other words, I thought that "the capability of the respiratory system" is better than "ther respiratory system's ability", because it's more clear to make the relation between two nouns and respiratory system is not human being so " 's " expression is incorrect. My guessing was wrong?

Please explain this. thanks.