What was the Iron Curtain?

A. a powerful agreement forged at Yalta at the end of World War II
B. the imaginary wall separating communist countries from democracies
C. the security arrangements that Stalin made to protect himself
D. a line of guns and canons that the Soviets spread across Eastern Europe

The rise of advertising in the 1920s. i am good with seeing how advertisements shape the roaring twenties and how it developed a new way of life through modern days. but i am not sure what the details of advertising in the 1920s were. if possible can you send me links (preferrably credential links) to sources that maybe show like the first company to start advertising through the radio, how advertising benefits (statistics graphs), etc.

The mongols were descendants of a. pastoral nomadic tribes b. tibetan tribes c. shang nobility

As a religious faith, candomblé appropriates beliefs from both a. african faiths and catholicism b. hinduism and catholicism c. hinduism and islam d. buddhism and catholicism