Explanation

(c)
Species having the same number of electron, have same bond order.
[table] Species | Number of electrons ; $CN^{-}$
$O_{2}^{-}$
$NO^{+}$
$CN^{-}$ | 6+7+1=14
8+8+1=17
7+8-1=14
6+7-1=12 [/table]
Since, $CN^{-}$ and ${NO}^{+}$ have same number of electrons, they have same bond order, $i.e$., 3.
$CN^{-}$ or ${NO}^{+}$ = 14= $\sigma 1s^{2},\ _{\sigma}^{*}1s^{2}\ ,\sigma 2s^{2},\ _{\sigma}^{*}2s^{2},\sigma 2p_{z}^{2}\ ,\ \pi 2p_{x}^{2} \approx \pi 2p_{y,}^{2}$
Bond order = $\frac{N_{b - \ }N_{a\ }}{2}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ = \frac{10 - 4}{2} = 3.$