The area of a rectangle is 99 square units its width measures 9 units find the length of its diagonal

The conjugate bases of most weak acids are weak bases.
The only conjugates that are strong bases are those of extremely weak acids, like water (pKa = 14), for which OH- is the conjugate base.
"The conjugate base of a relatively weak weak acid is a relatively strong weak base, and the conjugate base of a relatively strong weak acid is a relatively weak weak base."
NH2- is the conjugate base of an extremely weak acid, NH3 (pKa = 35). On the otehr hand, CN- is the conjugate base of a moderately weak acid, HCN (pKa = 9.2), so it's a moderately weak base.