Which of the following is not a semiconductor?

A semiconductor, any of a class of crystalline solids intermediate in electrical conductivity between a conductor and an insulator.

Graphite is an electrical conductor, not a semiconductor. The C atoms in graphite are arranged in parallel planes with hexagons in the planes (strong bond - sp² hybridization), and a pi (weak) bond between the planes. This pi bond gives the free electons for electrical conduction for graphite.