Assertion. Diamond is the hardest possible substance and is a network covalent solid.
Reason. All the C atoms in diamond are `sp^(3)` hybridised.
A. If both assertion and reason are true, and reason is the true explanation of the assertion.
B. If both assertion and reason are true, but reason not is the true explanation of the assertion.
C. If assertion is true, but reason is false.
D. If both assertion and reason are false.