____________ is a non-metal which can conduct electricity.
(A) Carbon
(B) Nitrogen
(C) Oxygen
(D) Sulphur

Hint: Nonmetal which can conduct electricity belongs to group 14 of the periodic table. It has atomic number 6. Valency is 4. It forms four covalent bonds. It exhibits the property of catenation. It exhibits many allotropic forms. Diamond and graphite are crystalline forms of it. Graphite has a layered structure. Graphite conducts electricity.

Complete step by step solution:
-Carbon belongs to group 14 in the periodic table.
-atomic number of carbon is 6. electronic configuration in ground state is \[1{{s}^{2}}2{{s}^{2}}2{{p}^{2}}\]. Electronic configuration of carbon in excited state is $1{{s}^{2}}2{{s}^{1}}2{{p}^{3}}$
-Carbon differs from rest of members from its group because of its smaller size, higher electronegativity, higher ionization enthalpy, unavailability of d orbitals.
-in carbon only s and p orbitals are available for bonding hence it can accommodate only four pairs of electrons.
-Carbon atoms have a tendency to link with one another via covalent bonds and form rings and chains. This property is called catenation.
-due to the property of catenation, carbon exhibits many allotropic forms both crystalline and amorphous.
-Diamond and graphite are crystalline forms of carbon.
-Graphite has a layered structure. Each layer is composed of planar hexagonal rings of carbon atoms. Each carbon atom in a hexagonal ring undergoes \[s{{p}^{2}}\] hybridization and makes three sigma bonds with neighbouring carbon atoms. The fourth electron forms a pie bond. The electrons are delocalized over the entire sheet. As electrons are mobile and therefore graphite conducts electricity along with the sheet.

Hence, the answer to this question is option (A).

Note: Due to the property of catenation and ability to form pi bonds, carbon can exhibit allotropic form. In diamond, each carbon atom undergoes $s{{p}^{3}}$hybridization and is linked to four other carbon atoms. Diamond has extended covalent bonding so it is the hardest substance on earth and it does not conduct electricity as it does not have free electrons. Graphite has one free electron which is responsible for conducting electricity.