Which among the following is a physical property of molecular solids?

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

Choose the correct option for crystalline solids based on the following statements:
$(1)$ They do not have a sharp melting point.
$(2)$ They gradually soften upon heating.
$(3)$ They have an irregular three-dimensional arrangement.
$(4)$ They show a rapid change in volume upon heating.

The ability of a substance to assume two or more crystalline structures is called

Give the classification of crystalline solids.

Which one of the following is the most correct statement?