Identify the pair of isosters among the following:

Atoms, molecules, or ions with the same number of atoms and valence electrons as one another are said to be isosteres.
Isomer refers to molecules or ions having the same number of atoms and the same number of electrons. For instance, the molecules ${\mathrm{N}}_2\mathrm{O}$ and ${\mathrm{CO}}_2$ are isosters and each have three atoms and 22 electrons.
The number of atoms and electrons in CO and "${\mathrm{N}}_2$" molecules is the same.