Answer : The correct answer is : The molecular solids would have the lowest boiling point because of WEAK INTERMOLECULAR FORCES.
Molecular solids :
These are solids , which are made up of molecules and sometimes atoms ( Noble gases , since they are inert ) . Hence the unit of molecular solid is a molecule . The bonding in molecules are covalent bonds which are strong bonds.
In molecular solids , molecules are held together by weak intermolecular forces or Van der Waal's forces like Dispersion forces , dipole-dipole forces , hydorgen bonds etc . Due to which molecular solids are soft and vaporize easily.
Since the forces operating between two molecules are weak , they are easily overcome by providing small heat , Hence they start boiling at low boiling point and have less heat of vaporization.