(A) is only one of the supporting points of the passage but not the main point. The passage overall is structured to describe "grand theories," discuss the reasons for the decline of "grand theories," and argue for an alternative historical perspective "that seeks to include the particular and unrepeatable details of historical events.." that would "allow for the possibility of historical explanation without viewing history as fully determined." Since this is the main argument that the author is making, we can conclude that it is the main point of the passage, i.e. the decline of grand theories demonstrates the importance of recognizing the role of historical contingency.
