Answer:
The answer is option A.
Explanation: After the end of WW2 Germany was divided into two main portion which were American controlled Germany and Soviet controlled Germany.There were also British and French occupied zone. But Berlin was deep inside into the Soviet controlled area which was also divided into four zones. But in 1948 the Soviet Union wanted whole Berlin for them. So they closed all the railway,roads,canals everything from western occupied Germany to western occupied Berlin in order to stop all supplies for them. That step rose tension on both side. Americans didn't want to leave Berlin. So they decided to stand tall. So they started to supply all the materials through air. This effort known as Berlin Airlift. This effort stopped possibly turning of hot war from cold war.