Sentence Correction

There is no agreement at present on what function, if any, certain herbs like gingko bilboa have in slowing the deterioration or improving memory.

(A) in slowing the deterioration or improving
(B) in the improvement or slowing of the deterioration of
(C) in slowed or improved deterioration of
(D) in the improvement to or the slowing of the deterioration of
(E) in slowing the deterioration of or improving

OA E

again I choose E, but I'm not sure of the rule pertaining to the things like "deterioration OF" followed by OR