Question

Why are turning points important in the process of periodization?

Answer 1

A turning point is a specific, significant moment when something begins to change. Turning point in the history is an event followed by big and important change (political change, social change, ...). Periodization is determining why and how historians divide up history.
Turning points are important in the process of periodization because they mark the beginning and ending of different periods (C).

Answer 2

The answer is:

c) they mark the beginning and ending of different periods.

Turning points are points in history where periods had a dramatic change, where times of changes for the different historic periods, for example, a turning point was the fall of Rome, it initiated the new organization of the western world, the eastern roman empire kept going for a while, but the absence of the Roman empire led to the birth of different little soveraign reigns.