Which among the following forces of attraction is developed between polar and non-polar molecules?

In which types of substances are intermolecular (van der Waals) forces present?

$A$ solid melts at a temperature above $100\,^oC$ and is a non-conductor of electricity in both solid and molten states. It is soluble in hydrocarbon solvents. What is the most likely structure of the solid?

Dry ice is an example of

The ionic compound $BaSO_4$ is insoluble in water due to

Electricity does not pass through ionic compounds in which of the following states?