What BEST explains what Bertrand Russell meant when he wrote, “This clears up two millennia of muddle-headedness about existence, beginning with Plato.”

Russell is saying that his argument clarifies a long-standing confusion about the philosophical idea of existence. “Two millennia” refers to roughly the span since Plato, and “clears up” means resolving or explaining the muddle—not dismissing Plato or claiming that nobody else wrote philosophy. Choice C best captures that claim, though “all” is stronger than the quotation strictly requires.

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