When the Soviet Union Denied the United States, Britain, and France

When the Soviet Union denied the United States, Britain, and France access to Berlin in 1948, President Truman responded by

A) asking the United Nations to intervene.
B) denying the Soviets access to West Germany.
C) declaring that an iron curtain had descended across Central Europe.
D) organizing a gigantic airlift of supplies to Berlin.
E) sending an armed convoy to Berlin.