Since there isn't any options provided I will write down all the countries that formed Yugoslavia so hopefully you can get the right answer.
Yugoslavia was formed out of six countries: Serbia, Croatia, Bosnia and Herzegovina, Macedonia, Slovenia, and Montenegro, all of which had the prefix SR in front of the name of the federal country, which means Socialist Republic.
These countries formed Yugoslavia after the World War II, and the foundations of the new country were laid on the Slavic ancestry of the people of those countries. The leader of the country, until 1980, was Josip Broz Tito, which was a leader respected all around the world, and who managed until he was alive to keep together and make brotherly nations of the nations that previously despised each other.
