I'm really confused between A and D too and can't still understand why A is wrong.

I chose A. The reason why I thought D was wrong is "widely accepted theory" part. The author said it has "gradually" won accepted (Line 20) rather than widely accepted. I think gradually accepted and widely accepted are totally different.

So how is it possible D is the right answer?

And why is A wrong?

Please someone enlighten me.

Thanks!

http://classic.7sage.com/lsat_explanations/lsat-42-section-3-passage-4-questions/