已知：HCN(aq)与NaOH(aq)反应的△H=-12.1 kJ·mol^-1；HCl(aq)与NaOH(aq)反应的△H=-55.6 kJ·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. +43.5 kJ·mol^-1

D. +67.7 kJ·mol^-1