Which of the following solids is not a molecular solid?

Which of the following possesses a layered crystal structure?

$A$ pure crystalline substance,on being heated gradually,first forms a turbid-looking liquid and then the turbidity completely disappears. This behaviour is the characteristic of substances forming

Which one of the following is a molecular crystal?

Which of the following is a primitive unit cell?

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.