请教９８７大全676(大全讨论中未有)

676. 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（A）

(E) a specially serious pollutant
because of diminishing the respiratory system’s ability to deal

Key:A

C为何不对，另外especially和specially在用法上具体有何区别？

Ususally, one would say ' x has the capability to do sth'  

'to deal' in A also makes this an active sentence.