Which action is an example of periodization

for apex it's D dividing china's history based on which dynasty ruled the country

i believe the answer would be 1.

on april 6, 1917, the u.s. joined its allies--britain, france, and russia--to fight in world war i. under the command of major general john j. pershing, more than 2 million u.s. soldiers fought on battlefields in france.