The Main Reason That So Much Is Known of Iron

The main reason that so much is known of Iron Age Assyria is that ______________.

A) the Assyrian Empire conquered all known literate territory at the time
B) other civilizations formed a united opposition and detailed their experiences
C) the Assyrians engaged in significant foreign policy and were methodical about compiling treaties
D) Assyrian rulers maintained records of their accomplishments
E) Herodotus wrote about it in his Histories