What happened after the battle of adrianople?

In one of the most decisive battles in history, a large Roman army under Valens, the Roman emperor of the East, is defeated by the Visigoths at the Battle of Adrianople in present-day Turkey. Two-thirds of the Roman army, including Emperor Valens himself, were overrun and slaughtered by the mounted barbarians.

b.

explanation:

he is racist

"oh, lets coppy china and build a great wall around bla bla bla.that way,we wont lose out to other countries." in the end, he did not build anything

the answer is a) high entry costs