Answer:
The correct answer is D. During Pax Romana, increased trade and commerce helped to unify the empire.
Explanation:
Pax Romana was a term for a period that went from 27 BC to 180 AD with relative peace and minimal expansion during the Roman Empire. The designation comes from the fact that the Roman government and its system of law pacified regimes, often with force, that previously suffered from strife between rival leaders. It was a relatively quiet period where the Romans suffered neither civil wars, as they did in the Late Republic, nor serious invasions, as they did during the Second Punic War two centuries earlier. During this time, the Roman Empire reached its peak in land use and its population increased to about 70 million people.
