The most accurate answer is D. Christianity became the new major religion of the empire.
As Christianity spread throughout the Roman Empire, it gradually gained popularity and acceptance, culminating in it becoming the state religion by the end of the 4th century. This shift had profound effects on Roman society, including changes in cultural practices, moral values, and political structures. While there were periods of persecution and coexistence with polytheistic beliefs, ultimately, Christianity's rise to prominence fundamentally transformed Roman society.