Which equation represents a reaction for which a base dissociation constant expression, \({K_b}\), can be written?

A.     \({\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH(aq)}} + {\text{N}}{{\text{H}}_{\text{3}}}{\text{(aq)}} \rightleftharpoons {\text{C}}{{\text{H}}_{\text{3}}}{\text{CO}}{{\text{O}}^ - }{\text{(aq)}} + {\text{NH}}_4^ + {\text{(aq)}}\)

B.     \({\text{HF(aq)}} \rightleftharpoons {{\text{H}}^ + }{\text{(aq)}} + {{\text{F}}^ - }{\text{(aq)}}\)

C.     \({\text{HCN(aq)}} + {\text{O}}{{\text{H}}^ - }{\text{(aq)}} \rightleftharpoons {\text{C}}{{\text{N}}^ - }{\text{(aq)}} + {{\text{H}}_{\text{2}}}{\text{O(l)}}\)

D.     \({\text{N}}{{\text{H}}_{\text{3}}}{\text{(aq)}} + {{\text{H}}_{\text{2}}}{\text{O(l)}} \rightleftharpoons {\text{NH}}_4^ + {\text{(aq)}} + {\text{O}}{{\text{H}}^ - }{\text{(aq)}}\)

D