Which type of solid crystals will conduct heat and electricity?

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.

The value of the heat of fusion of $NaCl$ is:

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 an amorphous solid?

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