Explanation
Correct answer: B.
Choice B is the best answer because it most logically completes the text’s discussion of how historians have treated rank-and-file (ordinary) workers in their analyses. In this context, "marginalize" means treat as unimportant or relatively powerless within a group or society. The text explains that according to Austin McCoy, historians have tended to treat "political, business, and labor leaders" as the "major actors" involved in making changes in organized labor in the period after the Second World War. By emphasizing the contributions of these leaders, historians have in effect minimized the contributions of ordinary workers, treating them as relatively unimportant and "nearly devoid of agency," thereby marginalizing them.
Why the other choices are wrong
Choice A
Choice A is incorrect. In this context, "epitomize" would mean either serve as an ideal example of something or make into an example of something, neither of which would make sense. In stating that historians have tended to characterize political, business, and labor leaders as the primary actors responsible for changes in the post-Second World War labor movement in a manner that minimizes the influence of ordinary workers, the text suggests that historians have tended to present ordinary workers as unimportant to or uninfluential within the movement, not that historians themselves serve as examples of ordinary workers, or that historians in their analyses have made ordinary workers into examples of the changes that occurred.
Choice C
Choice C is incorrect because in this context, "extol" would mean praise highly or glorify. The text states that historians have tended to present ordinary workers as being "nearly devoid of agency," thereby minimizing their importance. It therefore wouldn’t make sense to say that in doing so, historians have tended to praise or glorify them.
Choice D
Choice D is incorrect because "substantiate" would mean verify with evidence, and nothing in the text suggests that historians have verified rank-and-file workers or their contributions in their analyses. If anything, the text suggests the opposite, implying that by minimizing workers’ agency in organized labor, historians have likely overlooked evidence demonstrating their influence.