What is one major problem that has resulted from population growth in the 20th and 21st centuries?
A. Urban populations have fallen as people move to rural areas.
B. Many countries remain technologically underdeveloped.
C. Forced migrations have become more common than ever before.
D. Diseases can spread more easily because of urban overcrowding.

d and a is the correct anwsers

explanation:

the church governed the society after the empire fell.   constantine took charge of rome and ended the confusion which had over religion and made christianity as the only religion and that started ruling the roman empire. he also divided the empire into two and fortified the eastern part.   he ruled the eastern part.

the speech convinced americans that the ussr was an enemy, rather than an ally, which led to the creation of the truman doctrine.