WORLD CIVILIZATION

Detailed explanation-1: -The Roman Empire reached its greatest extent in 117 CE, under the emperor Trajan. When Trajan died, much of the territory he conquered in Mesopotamia was quickly lost, but from that point on, Rome’s frontiers became relatively stable.

Detailed explanation-2: -Officially declared optimus princeps ("best ruler") by the senate, Trajan is remembered as a successful soldier-emperor who presided over one of the greatest military expansions in Roman history and led the empire to attain its greatest territorial extent by the time of his death.

Detailed explanation-3: -In 1913, 412 million people lived under the control of the British Empire, 23 percent of the world’s population at that time. It remains the largest empire in human history and at the peak of its power in 1920, it covered an astonishing 13.71 million square miles-that’s close to a quarter of the world’s land area.