Which of the following statements is true for a crystalline solid?

Piezoelectric crystals are used in

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

What is a semiconductor? Describe the two main types of semiconductors and contrast their conduction mechanism.

Which of the following can act as a $p-$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.