The correct option is D Both (a) and (c)
Lesser the ionisation enthalpy, easier will be the formation of cation and easier will be the formation of ionic bond.
Larger the electron affinity, easier will be the formation of anions.
So, larger the force of attraction between the cations and anions, easier will be the ionic bond formation.
Smaller the size of the ions, lesser is the inter-nuclear distance and so greater will be the force of attraction, Hence, more will be the value of lattice energy.
Larger the lattice energy more stable is the ionic bond.