Which of the following compounds volatilises on heating?

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R.$
Assertion $A :$ Lithium halides are somewhat covalent in nature.
Reason $R :$ Lithium possesses high polarization capability.
In the light of the above statements,choose the most appropriate answer from the options given below:

$NaF$ is the highest melting halide because it is the most ionic in nature. This is because the chosen halide has:

What is the bonding nature in $LiCl$ bond?

Define polarization.

According to Fajan's rule,covalent bond is favoured by