Option A. amilitaryalliancemadeupofmultinationaldemocracies.
Explanation:
The western alliance was formalised into an organization theNorthAtlanticTreatyOrganisation(NATO),which came into existence in April 1949. It was an association of twelve states known as multinationaldemocracies.
Whicj declaref that armed attack on any one of them in Europe or Noth America would be regarded as an attack on all of them .
Each of these would be obliged to help each other.
With the breakage of warsaw pact , the countries of East Europe also joined NATO as a result of which its number has gone up to 28 and Russia is its participatory member.
The domino theory was a Cold War policy that suggested a communist government in one nation would quickly lead to communist takeovers in neighboring states, each falling like a perfectly aligned row of dominos.