The development of the hydrogen bomb by the united states and the u.s.s.r. was one result of

Athe cold war rivalry between the two nations in the 1950s.
Bthe world war ii alliance between the two nations in the 1940s.
Cbattles between the two nations during the vietnam war of the 1960s.
Ddisagreements between the two nations during the afghan war of the 1980s.