A) 2H2S(aq)Â Â Â Â
+Â Â Â Â
H2SO3(aq)   ?  Â
3S(s)Â Â Â +Â Â Â
3H2O(l)Â Â Â not balanced
number of atoms in reactant side is not equal to number of atoms
in product side.
B) NaOH(aq)Â Â +Â Â Â
HCl(aq)Â Â Â
?      NaCl(aq)
+Â Â H2O(l)Â Â Â Â balanced
number of atoms in reactant side is equal to number of atoms in
product side.
C ) CaCO3(s)   ?  Â
3CaO(s)Â Â Â Â +Â Â Â
CO2(g)Â Â balanced
number of atoms in reactant side is equal to number of atoms in
product side.
D ) Na2O(s)Â Â Â Â
+Â Â Â Â Â Â
HCl(aq)   ?  Â
NaCl(aq)Â Â +Â Â
H2O(l)Â Â Â Â not balanced
number of atoms in reactant side is not equal to number of atoms
in product side.