Which of the following solids is not a molecular solid?

Explain the terms 'fluids' and 'rigidity' in the context of states of matter.

What type of substance is $TiO$?

Low melting point is expected for a solid of which type?

Which of the following dopant is used in silicon to produce $p$-type semiconductor?

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.