An ionic bond ${\mathrm{A}}^{+}{\mathrm{B}}^{-}$ is most likely to be formed when :

An ionic bond ${\mathrm{A}}^{+}{\mathrm{B}}^{-}$ is most likely to be formed when the ionization energy of A is low and the electron affinity of B is high.

The amount of energy needed to free the gaseous atom's most loosely bound electron in order to create a cation is known as the ionization energy (IE). When an electron is added to a neutral atom or molecule in the gaseous state to produce a negative ion, energy is released. This is referred to as the electron affinity of an atom or molecule. More of a tendency to establish an ionic connection will occur when the electron affinity is high and the ionization energy is low.

Hence, option B is correct.