Sentence Correction

At the annualstock holders meeting, investors heard a presentation on the numerous challenges facing the company, including among them the threat from a rival's multi-billion dollar patent-infringement suit and the declining sales for the company's powerful microprocessor chip.

A. including among them the threat from a rival's multi-billion dollar patent-infringement suit and the declining sales for
B. which includes the threat of a rival's multi-billion dollar patent-infringement suit and declining sales of
C. included among these the threat from a rival's multi-billion dollar patent-infringement suit as well as a decline in sales for
D. among them the threat of a rival's multi-billion dollar patent-infringement suit and the decline in sales of
E. among these the threat from a rival's multi-billion dollar patent-infringement suit as well as the decline in sales for

[spoiler]OA is D.
Can somebody tell me : how the last phrase X<among them....sales of...microprocessor chip> is attached to the main clause.
I mean, X is a noun modifier, absolute phrase, adverbial modifier or something else.
[/spoiler]