The diagram shows the melting and boiling points of four different substances. Which substance has a melting point at ${-20}^{\circ }C$ and a boiling point at ${160}^{\circ }C$? Also identify the two substances having same boiling points.

From the diagram we have made the following table :

Substance	Melting point ${(}^{o}C)$	Boiling point ${(}^{o}C)$
A	$-20$	$80$
B	$-20$	$160$
C	$30$	$160$
D	$30$	$75$

From the table, the substances A and B both have melting point at $-{20}^{o}C$ and the substances B and C both have boiling point at ${160}^{o}C$.

The substance B and C have same boiling point.