What is CN- in this base and conjugate acid pair

A salt consisting of the conjugate base of a ____________ and conjugate acid of a ____________ will be neutral since neither will react with water. The salt consisting of the conjugate base of a ____________ and the conjugate acid of a ____________ will be acidic since the conjugate ____________ of a ____________ is acidic. A salt consisting of the conjugate base of a ____________ and the conjugate acid of a ____________ will be basic since the conjugate ____________ of a ____________ is basic. A salt consisting of the conjugate base of a ____________ and conjugate acid of a ____________ can be either acidic or basic depending on the relative Ka and Kb of the respective ions.

The word box includes: Weak base, base, strong base, acid, strong acid, weak acid