Which of the following countries did not join the capitalist block in 1945?

Poland

The correct answer is option (3) - Poland

U.S.A, Britain and France were a part of the Western Alliance which promoted the ideology of capitalism and democracy.

Warsaw Pact, composed originally of the Soviet Union (which consisted of 15 Soviet Socialist Republics) and Albania, Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, and Romania. These countries favoured the ideology of socialism and communism.

In response to the formation of NATO, the Eastern Bloc, led by the Soviet Union, formed its own military alliance known as the Warsaw Pact in 1955, which included countries from Central and Eastern Europe. It was led by the Soviet Union.  The eastern alliance, headed by the Soviet Union, was committed to the ideology of socialism and communism.