Which statement describes a property of covalent compounds?
they have a high boiling point because of strong intermolecular forces.
they have a low boiling point because of weak intermolecular forces.
they have a low melting point because of strong intermolecular forces.
they have a high melting point because of weak intermolecular forces.

 They have a low boiling point because of weak inter molecular forces.

That is because covalent bonds do not have a charge, meaning they are not reactive and are neutral. 

Correct  They have a low boiling point because of weak intermolecular forces.

Reason:
Covalent solids are characterized by weak intermolecular forces of interaction.  These forces are classified as follows:
1) Dipole-Dipole interaction
2) Dipole-induced dipole interaction
3) van der Waal's forces 
4) Hydrogen bonding

Since, magnitude of these forces are weak, covalent solids have low boiling point.