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

OA is D .

My question : I could clearly get down to A and D . However, i chose A over D because i thought modifier "among them the threat of a rival's multi-billion dollar patent-infringement suit and the decline in sales of " this way is incorrect. So is not the case as is apparent from the right modifier.

Could an expert help to explain what type of modifier it is, so i could use the same in other construct.

IN A the "threat" and "declining sales" are not parallel.

threat 'of' or threat 'from' ?
I choose E

For one thing, 'including' and 'among them' are redundant. So, A would have been better as:

including the threat from a rival's multi-billion dollar patent-infringement suit and the declining sales for
Or

Among them the threat from a rival's multi-billion dollar patent-infringement suit and the declining sales for

Also, C has parallel structures in:

1. the threat from X

2. decline in Y

thanks Ashish. Could you explain what kind of modifier it is :

"among them the threat of a rival's multi-billion dollar patent-infringement suit and the decline in sales of "

My 2 cents :

"sales of "is idiomatic than "sales for"

including among is redundant as in A.