We study history by Era because

An era is a span of time defined for the purposes of chronology or historiography, as in the regional eras in the history of a given monarchy, a calendar era used for a given calendar, or the geological eras defined for the history of Earth. We study history by era to make it easy to divide periods in the past.

hope it helps :)

please mark it the brainliest!

calvin taught his followers that human beings needed to follow strict rules to overcome their nature and do good. second choice