What is the modern era

Historical epochs.

Explanation:

Historical science is divided into several epochs. The modern era is a period in history that dates back to the First World War, 1918. Prehistoric age is the period from man's first appearance until the appearance of the letter when the ancient period begins. The ancient period in history lasted from the letter's appearance until 476, i.e., the Western Roman Empire's fall when the Medieval began. The Middle Ages lasted until 1492, i.e., the discovery of America. With the discovery of America, the historical epoch of the New Age begins and lasts until 1918.

b.

jim crow laws were enacted in northern states.