The Byzantine emperor Justinian's most lasting achievement was the a. permanent addition of Spain to the Byzantine Empire. b. collection and codification of Rome's ancient laws. c. sound financial footing on which he placed the Byzantine government. d. permanent addition of eastern Italy to the Byzantine Empire.

The answer is option B.

Explanation:

Justinian was the emperor of The Roman Empire between the years 527 and 565 during which he worked through the laws and rules that were accepted within the empire and modified/organized them under the name that is known as Justinian's Code. This helped bring balance and order and helped the empire to expand. So the answer is option B.

I hope this helps.

d. the right to establish a one-house legislature

"a government in which power is divided between state and national levels". federalism is a system of government in which entities such and state and province, share power with the national government.