http://classic.7sage.com/lsat_explanations/lsat-34-section-2-question-18/

18. Editorialist: The positions advanced by radical environmentalists often contain hypotheses that are false and proposals that are economically infeasible. But there is a positive role to be played even by these extremists, for the social and political inertia that attends environmental issues is so stubborn that even small areas of progress can be made only if the populace fears environmental disaster, however untenable the reasons for those fears may be.

Which one of the following most accurately expresses the main conclusion of the editorialist’s argument?

(A) The little progress that has been made in improving the environment is mainly due to the fear created by radical environmentalists.

(B) Radical environmentalists, by promoting their views, stimulate progress on environmental issues.

(C) Social and political inertia is most effectively overcome by an extremely fearful populace, regardless of whether its fears are well-founded.

(D) Radical environmentalists often put forth untenable positions in order to produce the fear that is required to bring about moderate reforms.

(E) Radical environmentalists advocate positions without regard for factual support or economic feasibility.

I am debating between A and B...

Why can't A be the correct answer choice? Is it because of the word mainly? or is it because answer choice (a) is saying that fear is the sufficient condition for the little progress to be made while the stimulus is saying that fear is the necessary condition for the progress?

Also, D seemed a little bit tricky but I eliminated that since we don't really know from reading the stimulus alone that environmentalists purposely said false things to create fear.. Is this the right way of thinking?

The correct answer choice is B, by the way. Thank you in advance!