ANS:B - no free electrons are present.

Diamond does not conduct electricity because no free electrons are present. Explanation:

1. Carbon Structure: Diamond is composed entirely of carbon atoms arranged in a tightly bound crystalline structure. Each carbon atom forms covalent bonds with four neighboring carbon atoms, creating a three-dimensional network structure.
2. Covalent Bonds: In diamond, each carbon atom forms strong covalent bonds with its neighboring atoms, resulting in a highly stable and rigid structure. These covalent bonds involve the sharing of electrons between atoms to form a stable molecular structure.
3. Absence of Free Electrons: In diamond, all the valence electrons of carbon atoms are involved in covalent bonding, leaving no free electrons to move freely within the crystal lattice. As a result, diamond does not have any charge carriers (free electrons or ions) that can conduct electricity.
4. Insulating Properties: Due to the absence of free electrons, diamond is an excellent electrical insulator. It does not allow the flow of electric current under normal conditions, even when subjected to an electric field.
5. Compact Structure and Crystalline Nature: While diamond's compact and crystalline structure contribute to its overall properties, such as hardness and optical characteristics, these factors do not directly affect its electrical conductivity. Instead, it is the absence of free electrons that primarily determines diamond's insulating properties.