On what factors does the magnitude of London dispersion forces depend?

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

$A$ number of ionic compounds e.g. $AgCl, CaF_2, BaSO_4$ are insoluble in water. This is because

Which substance has the strongest London dispersion forces?

Which of the following forces is involved in dinitrogen $(N_2)$?

The dipole-dipole interaction energy between stationary polar molecules and rotating polar molecules,respectively,is proportional to: [$r$ is the distance between the polar molecules]