I believe the answer is d but it could also be b
<span>In the Middle Ages, there were three heirs of Roman civilization. These three included: Byzantium, the Islamic Empire, and the territories of western Europe. The Byzantine Empire, founded by Emporor Constantine, was the first of these to inherit Roman civilization.</span>
Germanic tribes -- especially the Visigoths -- attacked the Roman empire and caused it to weaken.
There had been ongoing migration of Germanic tribes into Roman empire territory, that had a gradual weakening effect on the empire. The western tribes consisted of groups such as the Alamanni, Franks, Angles, and Saxons. There was also a large group of Germanic tribes known as the Goths. We speak of the Visigoths and Ostrogoths do distinguish between the western and eastern Goths. The Visigoths (western Goths) invaded the Roman Empire, and defeated Roman armies at the Battle of Adrianople in 378. Later, the Visigoths even invaded Italy and sacked the city of Rome in 410. So I suspect the answer your question is primarily looking for is the Visigoths.
