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I think it's saying that power is not every thing
The subordinate clause here is A, "as the layers of ash slowly compressed". Subordinate means that it cannot exist on its own, it has to be a part of the main, independent clause.
Singular noun is a noun that assigns to one thing, one person and one idea. Example: Boy, Girl, Father, Mother, Man, Doctor and so on.
America avoided the potential dangers that Bradbury seems to fear by staying true to the rights in the Constitution. America doesn't fear people who have knowledge and can question ideology, if anything they encourage it. And that is how America avoided some of the potential dangers in Fahrenhiet 451.
