Lets look at EC of each element one by one
#Argon
Electronic Configuration given by
[tex]\\ \sf\longmapsto 1s^22s^22p^63s^23p^6[/tex]
#Hydrogen
[tex]\\ \sf\longmapsto 1s^1[/tex]
#Berylium
[tex]\\ \sf\longmapsto 1s^22s^2[/tex]
#Helium
[tex]\\ \sf\longmapsto 2s^2[/tex]
Hence our answer is hydrogen.