When aqueous solutions of Na2SO4 and BaCl2 are mixed, a precipitate of BaSO4 forms according to the molecular equation
Na2SO4(aq) + BaCl2(aq) → BaSO4(s) + 2 NaCl(aq)
Which ion or ions are spectators when the reaction is expressed as a net ionic equation?
a) Na+ only
b) Na+ and Cl−
c) SO42− and Ba2+
d) Cl− only