What was an outcome of the north atlantic treaty?

a. the united states extended its policy on isolationism.
b. the soviet union blockaded berlin.
c. north korea attacked south korea.
d. all members agreed to treat an attack on one as an attack on all.
e. russia acquired poland and bulgaria.

The question is asking what an outcome of the North Atlantic Treaty was. The North Atlantic Treaty established NATO - North Atlantic Treaty Organisation - a group of countries that pledge to mutually defend each other, if they are attack by non-Nato countries ( and NATO countries are not supposed to be attacking each other either). The best answer is: D. All members agreed to treat an attack on one as an attack on all.