Answer:
Option: B. They mark the beginning and ending of different periods.
Step-by-step explanation:
Periodization tries to give weight to the way history is classified and organized through chronological periods. World history is enormous and dividing with each period differently to help historian and others to understand the past properly. Periodization is done to understand the period history with its political and other events during that particular period. They also help in telling the start and end of different periods.