What changes did the Roman Empire experience in the fourth century CE, and what were the causes of these changes?

The correct answer to this open question is the following.

Although there are no options attached, we can say the following.

The changes that the Roman Empire experienced in the fourth century CE completely changed the way the Roman Empire was ruled. The causes of these changes were the following.

Roman Emperor Constantine was persecuting Christians and sent them into the Colosseum to be devoured by the lions. But one night, he had a dream. An angel sent from the heavens told him to adopt Christianity in the empire and he would have fortune and success on the battlefield.

That is why Emperor Constantine proclaimed Catholicism as the official religion in the Roman Empire. Later, Constantine decided to move the capital of the Roman Empire to Constantinople (modern-day Istambul, Turkey). This new location was an important cosmopolitan city, with ports that served to increase trade and connect to other parts of the ancient world.  

because it took place after the war of 1812 had come to an end.

it would be a. that is the only one i could think of