Answer:
a, b and d are correct.
Explanation:
There are two types of attractive forces in covalent compounds:
Because intermolecular forces are usually quite weak compared with the forces holding atoms together within a molecule, molecules of a covalent compound are not held together tightly. Consequently, covalent compounds are usually gases, liquids, or low-melting solids.
Most covalent compounds aqueous solutions generally do not conduct electricity, because the compounds are nonelectrolytes.