Following the Mullikan scale, what parameters are required to evaluate electronegativity?

From the Mullikan scale, the parameters are required to evaluate electronegativity is Electron affinity and ionization energy.

According to Mullikan's, the electronegativity $=\frac{\text{ ionisation energy }+\text{ Electron affinity }}{2}$

Electron affinity can reflect the ability of an atom to gain electrons. The smaller the first electron affinity, the easier an atom gains electrons. The greater the electron affinity, the weaker is the ability of an atom to gain electrons. The ionization energy shows the ability of an atom to lose its electrons.

Hence, the option C is correct.