下列有关电解质溶液的说法正确的是

A．在Na2S稀溶液中：c (Na^＋)＞c (S^2^－)＞c (OH^－)＞c (H^＋)＞c (HS^－)

B．在Na2C2O4稀溶液中：c (Na^＋)＋c (H^＋)=" c" (OH^－)＋c (C2O4^2^－)＋c (HC2O4^－)

C．在含等物质的量的Na2CO3和NaHCO3的混合溶液中： 3 c (Na^＋)="2[c" (CO3^2^－)+ c (HCO3^－)+ c (H2CO3)]

D．在NaHSO3稀溶液中：c (OH^－)＋c (SO3^2^－)=" c" (H^＋)＋c (H2SO3)