Here, that’s the answer for your question
First telephone: Alexander Graham Bell, Antonio Meucci, Amos Dolbear.
First atomic reader: Robert Oppenheimer.
who made theory that made atomic power possible: Einstein.
First labor union: Samuel Gompers.
Father of the hydrogen bomb: Edward Teller.
Well, I have looked this up since you didn't add any options so I assumed a similar question would be found online. If your options are Germany, France, Britain and India, it would be India.