The electrical conductivity of semiconductors can be increased by:

Silicon is found in nature in the form of

Among solids,the highest melting point is established by

An example of a network solid is

Given below are two statements. One is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: Sharp glass edge becomes smooth on heating it up to its melting point.
Reason $R$: The viscosity of glass decreases on melting.
Choose the most appropriate answer from the options given below.

In $p$-type semiconductors,the conduction of electricity is primarily due to ....