Paraphrase the sentence below. As the Greeks sailed up the Nile River to the ancient cities of Memphis and Thebes, they asked native after native what the hieroglyphs meant. Not even the oldest Egyptians could tell them, for the language expressed in the hieroglyphs had already been dead for several hundred years. It had been replaced by Coptic, the language spoken by Christian Egyptians. And Coptic, in turn, was replaced by Arabic after the Arabs conquered Egypt in A. D. 642.