The correct option is B Diamond
The purest form of carbon is Diamond.
Diamonds are formed from carbon under the earth under conditions of extremely high temperature and pressure. Diamonds are generally found in small sizes. Some diamonds have eight sides. They form double pyramids. Some others have six sides. They form cubes.
In diamond, each carbon is joined to four other carbon atoms by single covalent bond. Out of the four valence electrons, each carbon atomshares one valence electron with the neighboring carbon atom to form a single bond. Carbon forms a giant molecule.This forms a three dimensional tetrahedral network of carbon atoms.