单选题 .  ①Until around 1930 few United States Civil War historians paid much attention to Southerners who opposed the 1861-1865 secession from the United States by a confederacy of Southern states. ②Southern historians clung instead to a notion of the South's unanimity in the face of Northern aggression. ③Only when scholars such as Lonn decided to examine this side of the war did historian of the Confederacy begin to recognize the existence of Southerners loyal to the Union (Unionists). ④While these early historians of Southern dissent broke new ground, they also reproduced Confederate authorities' negative view of loyalists as shady characters driven by dubious motives. ⑤Even Tatum, who took a largely sympathetic attitude toward loyalists, tended to lump them into nebulous categories, offering broad generalizations that ignored the particulars of Unionists' identities and experiences.
    ①This early-twentieth-century historiography nonetheless represented the leading research on dissent in the South until the 1960s and 1970s. ②Spurred by the advent of social historical methods, a new generation of historians found Unionists interesting as manifestations of the Confederacy's internal weaknesses. ③Focusing on the Appalachian Mountain and upper South regions of the Confederacy, these scholars argued that there was a profound divide among Southern Whites between those who benefited economically from slave-run plantations and those who did not. ④One such historian was Escott, who emphasized regional and economic conflict among Southerners. ⑤Escott cast Unionists and other dissenters as mountaineers who could not, by reason of economic and social alienation, identify with the proslavery Southern cause. ⑥This theme has heavily influenced the work of subsequent scholars, who commonly place Unionists at the extreme end of a continuum of class-based Confederate disaffection that was ultimately responsible for the South's collapse. ⑦Because the driving force behind such inquiries into loyalist history has been a desire to explain Confederate ideology, politics, and defeat, emphasis has been placed on the ways loyalist Southerners diverged from the political and economic mainstream of Confederate nationalism.
    ①Only recently have some Civil War historians begun to make Unionists and their experiences, rather than the Confederate state, the center of inquiry. ②These scholars have done intensive community and local studies of dissenting groups that take into account a range of social and cultural, as well as military and political, factors at work on the Southern home front. ③Hoping to better understand who remained loyal to the Union during the war, these historians have sought to explain the Civil War's underlying character, dimensions, and impact in particular counties or towns, especially in the upper South and Appalachia. ④This relatively new trend has stressed the particular, delved into the complexities of political allegiances on the home front, and, as Sutherland notes, highlighted "the gritty experience of real people."42.  The primary purpose of the passage is to ______