Truman's Response to the Soviet Blockade of West Berlin in 1948

Truman's response to the Soviet blockade of West Berlin in 1948 was to

A) divide the rest of Germany into occupation zones.
B) mass American troops on the Soviet border.
C) get the United Nations to officially protest.
D) launch a massive airlift of supplies into West Berlin.
E) meet with Stalin to diplomatically resolve the crisis.