Final answer:
In the context of an argument, the sentence from the excerpt of 'The Riddle of the Rosetta Stone' acts as evidence, demonstrating the incorrectness of a Greek writer's explanation about Egyptian hieroglyphs.
Step-by-step explanation:
The final sentence from the excerpt of The Riddle of the Rosetta Stone by James Cross Giblin serves as evidence within the argument structure. When the Greek writer Horapollo provided an inaccurate reason for why the picture of a goose represents the word "son", stating that it was because geese took special care of their young, this piece of information was incorrect. The inaccuracy of Horapollo's explanation provides evidence against the reliability of some Greek interpretations of Egyptian hieroglyphics. It shows that while the Greeks added their own explanations to the definitions, not all of these were based on factual understanding of the original Egyptian culture or language.