$NaCl$ and $C_6H_6$ exhibit which type of magnetism?

Silicon is found in nature in the form of

Why do solids have a definite volume?

Refractive index of a solid is observed to have the same value along all directions. Comment on the nature of this solid. Would it show cleavage property?

Which one of the following elements,when present as an impurity in silicon,makes it a $p$-type semiconductor?

Glass can be classified as $.......$.