The correct answer is C. the Cold War. It was after WW2 when Cold War just began and Berlin was split between the Eastern Bloc and the Western bloc. What happened was that the Soviets didn't want to allow Berlin to be supplied by the western forces so they put a blockade into the city and the US, working with Canadians and Brits, decided to send help using airplanes since it wasn't illegal and it couldn't be blocked.
