What is the prime mover of all glaciers

The figure is not necessarily a parallelogram because only one diagonal is bisected and only one pair of sides is congruent.

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!