Correct option is D
Diamonds are composed entirely of carbon atoms, which are arranged in a crystal lattice. Each carbon atom is covalently bonded to four other carbon atoms in a tetrahedral structure. These covalent bonds between the carbon atoms are extremely strong and provide diamond with its renowned hardness. This structure ensures that all four valence electrons of each carbon atom are used in bonding, making the diamond incredibly rigid and difficult to break.
Option (a) is incorrect because although diamonds are highly resistant to heat, they can be burnt at high temperatures in an oxygen-rich environment.
Option (b), while correct about the composition, does not explain the hardness of diamonds.
Option (c) describes the giant molecular structure but does not detail the bonding that causes hardness.
