1. what is the ultimate source of all the energy that powers your cells (and > 99.9% of all life on earth)? a. when did this process evolve and how do we know? b. when did appreciable levels of oxygen (o2) begin to build up in the atmosphere? c. why was there such a long delay between the dates in part 2a and 2b above?

Historians are researchers of the past or people who understand the history of people. with this field, they must possess qualities such as being unbiased, patient, efficient reader, has a knack for logic and critical thinking and reasoning, disciplined, open-minded, resourceful, with good analytical ability, good reasoning skills and problem solving!

The answer is d) rift

The answer to the first one is barometer.