Species with the same number of electrons (isoelectronic species) generally have the same bond order according to Molecular Orbital Theory.

• $\text{CN}^-$: The total number of electrons is $6 \text{ (C)} + 7 \text{ (N)} + 1 \text{ (negative charge)} = 14$ electrons. Its bond order is 3.
• $\text{NO}^+$: The total number of electrons is $7 \text{ (N)} + 8 \text{ (O)} - 1 \text{ (positive charge)} = 14$ electrons. Its bond order is also 3.

Let's check the other pairs:

• $\text{CO}$ has 14 electrons (bond order 3) while $\text{NO}$ has 15 electrons (bond order 2.5).
• $\text{O}_2^-$ has 17 electrons (bond order 1.5) while $\text{CN}^-$ has 14 electrons (bond order 3). Therefore, $\text{CN}^-$ and $\text{NO}^+$ are the pair with the same bond order.