Based on details from The Riddle of the Rosetta Stone, what is an effect of the hieroglyphs and the Greek alphabet appearing together on the slab?

It suggests others discovered the Rosetta Stone before the French and wrote on it.
It provides an opportunity to decipher the unknown hieroglyphs by matching them to the known Greek language.
It explains why the British are so determined to stop the French invasion of Egypt.
It proves the theory that the Egyptians had invaded and conquered Greece centuries before.