Which type of van der walls force is responsible for holding polar molecules together? london dispersion dipole-dipole hydrogen bonding gravitational force?

dipole-dipole

Explanation:

Polar molecules are formed as result of covalent bonds between atoms.

Dipole-dipole attraction are intermolecular bonds. Both London dispersion forces and dipole-dipole attraction are van der waals forces.

In dipole-dipole attraction, polar molecules (unsymmetrical molecules) line up such that the positive pole of one molecule attracts the negative pole of another. Example of such is found in HCl.