单选题：下列叙述 Na2S溶液的质子条件，正确的是（） A: [H+]+[Na+]= [HS–]+[S2-] +[OH–] B: [H+]+[HS–] +[H2S]=[OH–] C: [H+]+[Na+]= [HS–]+2[S2-] +[OH–] D: [H+]+[HS–] +2[H2S]=[OH–] 答案: [H+]+[HS–] +2[H2S]=[OH–] 5