The energy band gap (distance between the conduction band and valence band) in a conductor is

At absolute zero temperature, a semiconductor behaves like

Assertion $(A)$: When a wire of aluminium and another wire of silicon are heated from room temperature to $80^{\circ} C$,the conductivity of aluminium decreases and that of silicon increases.
Reason $(R)$: Aluminium has a positive temperature coefficient of resistivity and silicon has a negative temperature coefficient of resistivity.

The band gap in Germanium and Silicon in $eV$ respectively is

In semiconductors at room temperature,

When the temperature of a silicon sample is increased from $27^\circ C$ to $100^\circ C$,the conductivity of silicon will be