$A$ transistor is a/an

When a small amount of impurity atoms are added to a semiconductor,then generally its resistivity

When a battery is connected to a $P$-type semiconductor with a metallic wire,the current in the semiconductor (predominantly),inside the metallic wire,and inside the battery is due to which charge carriers respectively?

$A$ semiconductor is placed in an electric field. Let the number density of charge carriers be $n$ and the average drift velocity be $v$. If the temperature is increased,then:

Assertion: The number of electrons in a $p-$type silicon semiconductor is less than the number of electrons in a pure silicon semiconductor at room temperature.
Reason: It is due to the law of mass action.

Explain the concept of the hole in the semiconductor.