Although the new policy aims to increase efficiency, reducing costs, and enhancing employee satisfaction , some employees feel that the changes are too abrupt and poorly communicated.

The sentence uses "parallel structure". To be grammatically correct, all the verbs mentioned in the sentence [increase, reducing , and enhancing] should follow the same verb form. Each verb is in the infinitive form without "to" (the infinitive structure is to + V1). The correct structure here is therefore the base form of the verb(V1): "increase," "reduce," and "enhance.", which makes Option D the correct answer. 

The other options break this parallelism. Option A uses "reducing" and "enhanced," which are inconsistent. Option B introduces incorrect phrases like "reducing of costs" and "enhancing of." Option C starts well but ends with "enhancing," disrupting the verb pattern.