According to Fajan's Rule, small cation has more polarising power and larger anion has more polarisability. These small cations and larger anions favours covalent character.

A. $\mathrm{KF}>\mathrm{KI}$$-$False (Iodide is larger anion than fluoride)

 $\mathrm{LiF}>\mathrm{KF}-$True (Lithium-ion is smaller cation than potassium ion)

B. $\mathrm{KF}<\mathrm{KI}-$True; $\mathrm{LiF}>\mathrm{KF}-$True

C. ${\mathrm{SnCl}}_{4 }>{\mathrm{SnCl}}_2-$True(${\mathrm{Sn}}^{4+}$ is smaller than ${\mathrm{Sn}}^{2+}$); 

The ions with pseudo inert gas configuration prefers the covalent character.

$\mathrm{CuCl}>\mathrm{NaCl}-$True(${\mathrm{Cu}}^{+}\left(3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}3{\mathrm{d}}^{10}\right)$ ion has pseudo inert gas configuration)

D. $\mathrm{LiF}>\mathrm{KF}-$True; $\mathrm{CuCl}<\mathrm{NaCl}-$False

E. $\mathrm{KF}<\mathrm{KI}-$True; $\mathrm{CuCl}>\mathrm{NaCl}-$True