The $\mathrm{O}-\mathrm{O}$ the bond length in ${\mathrm{O}}_2,{\mathrm{O}}_2\left[{\mathrm{AsF}}_4\right]$ and $\mathrm{K}\left[{\mathrm{O}}_2\right]$ is :

The correct bond length order is, $\left.{\mathrm{O}}_2\left[{\mathrm{AsF}}_4\right]<{\mathrm{O}}_2<{\mathrm{K}}_2{\mathrm{O}}_2\right]$.

Bone order of  ${\mathrm{O}}_2, {\mathrm{O}}_2^{+}$ and ${\mathrm{O}}_2^{-}$ are $2,2.5$ and $1.5$ respectively. Greater is bond order lesser is.

$\begin{array}{l}\mathrm{O}-\mathrm{OB}.\mathrm{L}.:{\mathrm{O}}_2^{-}>{\mathrm{O}}_2>{\mathrm{O}}_2^{+}\\ \text{B.O. }{\mathrm{NO}}^{+}\left(3.0\right),\mathrm{NO}\left(2.5\right),{\mathrm{NO}}^{-}\left(2.0\right)\\ \text{ B.O. }\propto \frac{1}{\text{ B.L. }}\end{array}$

Hence correct option is A.