During the Middle Ages, the dominant religion of western Europe was A Eastern Orthodox Christianity.
B
Roman Catholic Christianity.
Roman Polytheism.
D) split between Islam and Judaism.

Roman Catholic Christianity.

Explanation:

Catholicism was established as the dominant religion of Western Europe in ancient times. The Edict of Milan in 313 first allowed the manifestation of Catholicism as a religion, only to become the state religion in 374. From then until today, Catholicism has become and remains the dominant religion in Western Europe. When we talk about other parts of Europe through the Middle Ages, Catholicism also dominated until the church schism in 1054 when parts of the Byzantine-controlled empire began to practice Orthodoxy. That was not the case with all Eastern European countries, but it is in most.

they thought they were   chrstian even though they were roman opening a r religous war and giving people hope