In the first paragraph of this passage, the author describes Dahl's democratic principle as an ideal of political equality, where everybody has an equal voice in decision-making. Dahl acknowledges that in the real world, "no society can guarantee perfect equality in the resources that may give rise to political influence." In other words, political equality is the ideal that democratic societies strive toward, even if they will never be able to reach perfect equality. "So actual systems can be deemed democratic only as approximations to the ideal."
Answer choice B is a good analogy because there is a musical score whose ideal tonality cannot actually be reached by any real world instrument. Instead, musicians can only strive toward the ideal and make their best approximations.
