The main purpose of Truman's Radio Address was A
To warn Americans of a possible nuclear war
OB. To explain the accomplishments of the U.S. in
nuclear research, and how this will impact the war
OC
To offer remorse for killing so many Japanese
OD. To explain the positive uses for nuclear power in
the post-war world

I don’t know but just try your best

A

Explanation:

Well before than people thought the earth was in the center of the universe (because it appears that the sun and moon are going around the earth when they set and rise) which was called geocentric. Even though at first Copernicus's ideas were quite controversial, eventually people moved to the heliocentric model.