Answer:
C. It has no delocalised electrons and each carbon atom forms four covalent bonds with other carbon atoms.
Step-by-step explanation:
- Diamond is composed solely by carbon atoms. As the difference of electronegativity between atoms is 0, diamond is a fully covalent compound.
- The lack of electrical conductivity stems from a lack of available electrons, this means that there are no delocalised electrons.
The information in the first point discards options A and D, while the second point discards option B. Thus the answer is option C.