Why A

I arrived at A based on the information in the first paragraph, lines 8-16. In those lines the author is saying that Dahl recognizes the hierarchical ordering inevitable in the government and how it will influence politics and then the author states, "the democratic principle of political equality is incapable of full realization" and that "actual systems can be deemed democratic only as approximations to the ideal." From these lines I inferred that although Dahl defends polyarchies, he is aware that they are limited in the extent to which they can embody the idea of democracy (A).