What was an outcome of the north atlantic treaty?

1.the united states extended its policy on isolationism.
2.the soviet union blockaded berlin.
3.north korea attacked south korea.
4.all members agreed to treat an attack on one as an attack on all.
5.russia acquired poland and bulgaria.

Which statement best describes the reason why the allies responded to the berlin blockade by airlifting supplies to the city? they did not have enough troops to attack the ussr. they controlled only the water routes to berlin. they controlled only one land route into west berlin. they did not want to use military force against the ussr.