Which of the following is an example of instantaneous dipole-induced dipole attraction?

Alumina $(Al_2O_3)$ is:

The enhanced force of cohesion in metals is due to

The lattice enthalpy of an ionic compound is the enthalpy change when one mole of an ionic compound in its solid state dissociates into its ions in the gaseous state. It is impossible to determine it directly by experiment. Suggest and explain an indirect method to measure the lattice enthalpy of $NaCl_{(s)}$.

For the two ionic compounds $CaO$ and $KI$,identify the incorrect statement from the following.

Which of the following is not correctly matched?