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

I picked E because of below -
If you read in slowing the deterioration of .... memory it is better than without OF as used in A.


X or Y ....Z
Approach X....Z & Y....Z both should make sense separately .....