已知：HCN(aq)与NaOH(aq)反应的△H=-12.1kJ·mol^-1；HCl(aq)与NaOH(aq)反应的△H= -55.6kJ·mol^-1。则HCN在水溶液中电离的△H等于(　　)

A、-67.7 kJ·mol^-1

B、-43.5 kJ·mol^-1

C、+43.5kJ·mol^-1

D、+67.7kJ·mol^-1