The intrinsic semiconductor becomes an insulator at

$Sn, C, Si$,and $Ge$ are all group $XIV$ elements. Yet,$Sn$ is a conductor,$C$ is an insulator,while $Si$ and $Ge$ are semiconductors. Why?

Read the following statements carefully:
$Y:$ The resistivity of a semiconductor decreases with an increase in temperature.
$Z:$ In a conducting solid,the rate of collision between free electrons and ions increases with an increase in temperature.
Select the correct statement from the following:

Give a brief explanation of solid state semiconductor electronics.

If the lattice constant of this semiconductor is decreased,then which of the following is correct?

Assertion : The resistivity of a semiconductor increases with temperature.
Reason : The atoms of a semiconductor vibrate with larger amplitude at higher temperatures,thereby increasing its resistivity.