Sentence Correction

The board of trustees, worried about the Neith corporation's rising debts, instructed Neith's CEO to not only downsize significantly, to lay off over 5000 employees around the country, but terminating as well the Neith's relationship with Arachne Unlimited, who in the past year were draining valuable funds from the Neith.
(A) to not only downsize significantly, to lay off over 5000 employees around the country, but terminating as well the Neith's relationship with Arachne Unlimited, who in the past year were
(B) to not only downsize significantly, to lay off over 5000 employees around the country, but also to terminate the Neith's relationship with Arachne Unlimited, which in the past year were
(C) not only to downsize significantly, to lay off over 5000 employees around the country, but also terminating the Neith's relationship with Arachne Unlimited, who in the past year was
(D) not only to downsize significantly, laying off over 5000 employees around the country, but also to terminate the Neith's relationship with Arachne Unlimited, which in the past year was
(E) not only to downsize significantly, laying off over 5000 employees around the country, but also terminating the Neith's relationship with Arachne Unlimited, who in the past year were


OA is D

With the long sentence, what have made option D the best. I want a clear analysis on this by an EXpert.