Which of the following was the cause of the united states' and great britain's berlin airlift? russia was trying to take more territory. russia was blocking supply routes. russia was the north koreans. russia wanted to fight great britain over new trade routes.

Russia was blocking supply routes. 

Russia believed that blocking the supply routes would help cut the US and Great Britain supplies in Berlin.  They thought that this move can be one ground to let Allies get off Berlin. They tried to block all the possible routes where the US and Great Britain can get supplies for their own divided zones in Berlin. The Berlin Airlift bridged the trouble on traveling supplies.