Why was the end of the 19th century know as the "Age of Imperialism"? A African countries aggressively expanded their empires in United States
B European countries aggressively expanded their empires in Asia and Europe
C African countries aggressively expanded their empires in Asia and Africa
D European countries aggressively expanded their empires in Asia and Africa

It came into use after 1850. It was a new kind of European expansion which was not marked by widespread settlement. Its objective was to control territories for political and economic reasons and for national prestige. The late 19th century is often called the Age of Imperialism

i believe the correct answer is option b. most eastern european nations joined nato.

though i could be wrong, option d. the eastern european nations were granted complete independence, would be another choice.

hope this ! : )

i would say your answer is a)

sorry if im wrong