If the energy gap of a substance is $5.4 \ eV$,then the substance is

$C$ and $Si$ both have the same lattice structure,having $4$ bonding electrons in each. However,$C$ is an insulator whereas $Si$ is an intrinsic semiconductor. This is because:

Electrical conductivity of insulators is

Regarding a semiconductor,which one of the following is wrong?

The energy band diagrams for three semiconductor samples of silicon are as shown. We can then assert that :-

The class of materials having the largest band gap in the following is