Why was the middle ages period once referred to as the "dark ages"

The Dark Ages is a term often used synonymously with the Middle Ages. It refers to the period of time between the fall of the Roman Empire and the beginning of the Italian Renaissance and the Age of Discovery. ... Debate continues to rage among historians over whether the Middle Ages were, indeed, dark or not.

protected civil liberties and outlawed slavery in the new territories.

the answer should be a. the sui empire, the tang empire extended from korea in the west to manchuria in the east.