Answer:
He decided the three hieroglyphs must represent the name of Thothmes, the "Child of Thoth," a pharaoh who ruled Egypt from 1501 to 1447 B.C.
Step-by-step explanation:
Thesis claims cannot be made or proposed without any clear evidence which supports the claim. And in doing so, this will provide validity to what claim an author has made.
The thesis statement states that James Cross Giblin gave "clear explanations of the important historical figures in ancient Egyptian history in The Riddle of the Rosetta Stone." Now, to support this thesis statement, the evidence of how Champollion found out about the three hieroglyphs that must have represented the name of Thothmes, "the child of Thoth". This statement seems to provide genuine evidence for the argument/ implied claim that Giblin made about the important historical figures in Ancient Egyptian history.