What was Churchill referring to with the term iron curtain is d) the separation of Western Europe and communist Eastern Europe
Winston Churchill used the term "Iron Curtain" in his 1946 "Sinews of Peace" speech to describe the division of Europe into two spheres of influence: the Western democracies and the Soviet-dominated Eastern Bloc. It symbolized the ideological and political barrier that had descended across the continent following World War II.
Therefore, based on the historical context and Churchill's own words, the "Iron Curtain" specifically referred to the division of Europe between the West and the Soviet-controlled East