Two elements A and B have similar chemical properties. They don't form solid hydrogencarbonates, but react with nitrogen to form nitrides. A and B, respectively, are :
(1) Li and Mg
(2) Na and Ca
(3) Na and Rb
(4) Cs and Ba
(1) Li and Mg
(2) Na and Ca
(3) Na and Rb
(4) Cs and Ba