GmatKiss wrote:Scientific interest in providing suitable habitats for bottom-dwelling animals such as river clams arises not because they are important sources of human food but from their role as an integral link in the Aquatic food chain.

(A) not because they are important sources of human food
(B) although they are not an important sources of human food
(C) not in that they are important as human sources of food
(D) not from their importance as a source of human food
(E) not from being important sources of food for human beings

IMO:A

IMO:E

I think D is the best answer because it parallels "not from" twice... Answer E is similar but I don't think "being important" parellels "their role" as well as "their importance."

(A) not because they are important sources of human food
(B) although they are not an important sources of human food
(C) not in that they are important as human sources of food
(D) not from their importance as a source of human food (CORRECT)
(E) not from being important sources of food for human beings

D and E give the meaning, but D is better, I think. When I made the sentence with a simpler form;

D)... arises not from their importance as a source but from their role as an ...
E)... arises not from being important sources of food but from their role as an ...

I am not good at SC, if my explanation is wrong, please let me know

E

OA ??

Looking at the sentence after the underlined part, "but from their", not because ___ but from their ___ are not parallel.
Also, not from ___ but from ___ is idiomatic.

IMO: D

IMO D

maintains the parallalism.

please explain how other options are eliminated!

GmatKiss wrote:Scientific interest in providing suitable habitats for bottom-dwelling animals such as river clams arises not because they are important sources of human food but from their role as an integral link in the Aquatic food chain.

(A) not because they are important sources of human food
(B) although they are not an important sources of human food
(C) not in that they are important as human sources of food
(D) not from their importance as a source of human food
(E) not from being important sources of food for human beings

IMO:A

the structure should be parallel. not from ___ but from ___

Eliminate A,B and C.
Now let us consider D and E. First of we should eliminate the answer choices with "being" whenever we can. But this it not the only thing. D is a better choice than E on the grounds of parallelism.
D says "not from their importance as a source of human food but from their role as an integral link in the Aquatic food chain.". it is a much better construction than E "not from being important sources of food for human beings but from their role as an integral link in the Aquatic food chain."