Which structure has delocalised $\pi$-electrons?

In the resonance hybrid of an ozone $(O_3)$ molecule, the $O-O$ bond length is: (in $pm$)

The correct stability order of the following resonance structures of $CH_3-CH=CH-CHO$ is:

The correct statement$(s)$ about $O_3$ is (are)
$A$. $O-O$ bond lengths are equal.
$B$. Thermal decomposition of $O_3$ is endothermic.
$C$. $O_3$ is diamagnetic in nature.
$D$. $O_3$ has a bent structure.

Draw the resonance structures of $N_2O_4$,state its shape,and indicate the bond angles and bond lengths.

What is the number of Lewis structures for $NO_2^{-}$?