Which electron transition represents a gain of energy?
Afrom 2nd to 3rd shell
Bfrom 2nd to 1st shell
Cfrom 3rd to 2nd shell
Dfrom 3rd to 1st shell
Afrom 2nd to 3rd shell
Bfrom 2nd to 1st shell
Cfrom 3rd to 2nd shell
Dfrom 3rd to 1st shell