Final answer:
After World War II, disagreements between the Western Allies and the Soviet Union were primarily rooted in ideological differences and the vision for Europe's future, leading to the long-standing Cold War. The correct option is A.
Step-by-step explanation:
The post-war issues that caused the Western Allies and the Soviet Union to disagree included economic disparities in war reparations, ideological differences and political tensions, and conflicting visions for the reconstruction and political future of Europe. These tensions led to the development of the Cold War, characterized by an arms race, espionage, and influence battles in newly formed sovereign states.
Immediately after World War II, the United States and the Soviet Union disagreed on the administrative approach for postwar Europe, with the U.S. promoting Western-style democracies and the Soviets pushing for Soviet-aligned Communist governments. The desire of the Soviets to create a pro-Russian buffer zone and differing economic systems further fueled the divide, as the US sought to encourage capitalist prosperity through economic aid as a response to the spread of socialism and communism.
The conflict between communism and capitalism defined the postwar geopolitical landscape, leading to persistent economic and political tension between the competing superpowers. Hence the correct option is A.