The Cold War was a conflict primarily between:

The Cold War (approximately 1947-1991) was a prolonged period of geopolitical tension primarily between two superpowers: the United States of America (USA) and the Union of Soviet Socialist Republics (USSR, or Soviet Union). It was called a "cold" war because the two sides never engaged in direct large-scale military combat against each other, though they competed intensely through arms races, proxy wars, espionage, propaganda, space exploration, and ideological rivalry.

The conflict was fundamentally ideological. The USA championed capitalism, liberal democracy, and free-market economics, while the USSR promoted communism, one-party rule, and a centrally planned economy. Each superpower sought to expand its sphere of influence across the globe, leading to interventions and proxy conflicts in Korea, Vietnam, Afghanistan, Cuba, and numerous African and Latin American nations.

The USA and Britain were actually close allies throughout the Cold War, both being members of NATO. While the USA and China had tensions (particularly after China's communist revolution in 1949), the Cold War is defined by the US-Soviet rivalry. The USA and Germany were not primary opponents; in fact, West Germany was a US ally, while East Germany was a Soviet satellite state - Germany was itself a product of Cold War division.

The correct answer is the USA and USSR, the two superpowers whose rivalry defined the Cold War era.