Which one of the following most accurately expresses the main point of ... ...

Which one of the following most accurately expresses the main point of the passage?
(A) Although the secondary substances in plants do not take part in the plants’ basic biological processes, these substances operate as natural defenses against damage and destruction by insects.
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Dec 2012 LSAT (PT 68): Reading Comprehension