求助OG 8-43

I feel confused about option A, why the correct answer is not C.

in lines24, 'in 1977, 34 percent of government clerical workers were represented by a labor organization, compared with 46 percent of government professionals, 44 percent of government service workers, and 41 percent of government blue-collar workers. ‘compared with 不是与什么相比吗？

该句本文中意为：与之相比而言或是相对应的是。。。下述的各个percentage