IMO
B
I am not an expert, but trying to put some of my points.
This is a nice question ,and I guess this is an evaluate type question("best explain how the consumption..." ).Even though in this question, answer is very straight forward, it becomes very difficult at times when options are presented in the form of statements rather than question. I use to face a lot of problem in such question until I got a great tip from some anonymous ANGEL

. When ever you see statement rather than question, convert the sentence into question. Now according the Powerscore bible you should provide polar answers to the question and see if the answer makes the argument/conclusion weak or strong. If there is no effect ,probably the option is an incorrect choice.You should do this test only on contender options else you may run out of time. For the sake of clarity , let's convert the statement to question,provide polar responses and see its effect on the conclusion / argument.
Conclusion : Organic food were considered good because of absence of pesticides in them.
A) Did organic food marketing group determine that soil in which Organic "fruits and vegetables" are grown was ever treated with pesticides? (Who cares ???
if the group determined or not.)
B) Does the ingestion of pesticide inhibit molecular function that are primarily responsible for body's development of certain immunities...... (if you say "Hell NO" ---> it's weakening the argument & when you say "Hell Yes"-->it's supporting the argument ) Do not get fooled by this kind of tricky statement ever again
C) Are adverse effect noticed by individuals who ingested them in small quantity? YES / NO ---> does not matter (degree of "adverse effect " may vary from individual to individual or it may be possible whatever the person consider adverse is not serious on medical grounds )
D) Are pesticide commonly used .....? YES / NO ---> does not matter
E) Whether the subjects knew about the kind of food they are eating ....? YES / NO ---> does not matter
Apply the concept of questioning on statements (in EVALUATE TYPE QUESTIONS ONLY), and hopefully the answers will come out in flash!!!