C, Si and Ge have same lattice structure. Why is C insulator while Si and Ge are semiconductors ?

C has the tendency of catenation. C is electrically neutral. The band gap of C is as high as 5.5 eV. All of the above.

The band gap of C is as high as 5.5 eV.

IT is due to the band gap of C that it is categorised as an insulator.