Since the choices are missing, I will tell you why non-metals tend to form covalent bonds. You can then link this answer to the best fit choice.
Ionic bond is only formed due to an electrostatic attraction force between ions of opposite charges which cannot happen in case of non-metals whose ions are mostly anions.
On the other hand, a covalent bond is formed due to electrons being shared among different atoms. This conditions is satisfied for the bonds between non-metals
