Which of the following materials is not a semiconductor?

Which among the following is a ferromagnetic substance?

The phenomenon in which a substance exists in more than one form is called ......

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

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.

Which of the following is a molecular solid?