The berlin blockade was:
a. a barrier erected by allied forces in postwar berlin to shield them from angry protests of starving residents.
b. a means for the united states to justify its threat to mobilize allied forces stationed in turkey.
c. erected because the united states threatened to invade the soviet union.
d. the reaction by the soviet union to the establishment of a separate currency in western berlin's occupied zones.
e. a temporary defensive measure by the united states that was soon taken down.

Among the options shown here:

d. the reaction by the Soviet Union to the establishment of a separate currency in western Berlin's occupied zones.

Explanation:

France, Great Britain and the United States, the Western allies, announced on June 7,  1948, that they´d go on with the creation of West Germany. The Soviet Union did not agree with the idea and started to block terrestrial access to the German capital since June 24. The US and its allies launched an airlift to provide supplies to the encircled parts of Berlin under Western control. It lasted around a year.