Read the excerpt from The Riddle of the Rosetta Stone.

The Ptolemys kept their Greek culture, including their language, but they also respected the customs and religious beliefs of the native Egyptians. So it was only natural for the priests’ statement to have been carved in both Greek and Egyptian on the Rosetta Stone.

What signal word helps readers identify evidence of a cause-and-effect relationship in this excerpt?

but
also
so
and