Why did the U. S. and Soviet Union agree to stop detonating bombs in 1963?

Nuclear Test-Ban Treaty, formally Treaty Banning Nuclear Weapons Tests in the Atmosphere, in Outer Space, and Under Water, treaty signed in Moscow on August 5, 1963, by the United States, the Soviet Union, and the United Kingdom that banned all tests of nuclear weapons except those conducted underground.

Explanation:

i believe your answer is d)

on april 6, 1917, the u.s. joined its allies--britain, france, and russia--to fight in world war i. under the command of major general john j. pershing, more than 2 million u.s. soldiers fought on battlefields in france.