Which intermolecular force is common to all polar molecules but not nonpolar molecules? dispersion forces dipole-dipole forces hydrogen bonding x-forces none of the above?

            Dipole-Dipole Forces are common to all polar molecules but not non polar molecules.

Explanation:
                   An Asymmetrical molecule having a region of high electron density (partial negative) and lower density (partial positive) interacts with its neighbor molecules through Dipole-Dipole Interactions. The partial positive part of one molecule interacts with the partial negative part of another.

Example:
               Acetone having a partial positive carbon (of carbonyl group) and partial negative oxygen interacts through Dipole-Dipole forces. Hence, acetone does not involves Hydrogen Bond interactions.

Although the diagram is not shown, i know that the convection is heated by a the core.