In the $HCOO^-$ anion,the two carbon-oxygen bonds are found to be of equal length. What is the reason for this?

The stability order of the following resonance structures is:
$I. CH_2=CH-CH=O$
$II. CH_2^+-CH=CH-O^-$
$III. CH_2^--CH=CH-O^+$

Given below are two statements :
Statement $I$ : Experimentally determined oxygen-oxygen bond lengths in the $O_3$ are found to be same and the bond length is greater than that of a $O=O$ (double bond) but less than that of a single $(O-O)$ bond.
Statement $II$ : The strong lone pair-lone pair repulsion between oxygen atoms is solely responsible for the fact that the bond length in ozone is smaller than that of a double bond $(O=O)$ but more than that of a single bond $(O-O)$.
In the light of the above statements,choose the correct answer from the options given below:

During the formation of the dimer $N_2O_4$ from two molecules of $NO_2$,the odd electron on the nitrogen atom of each $NO_2$ molecule pairs up. What is the resulting structure?

All bonds in benzene are equal due to

In a benzene molecule,all $C-C$ bond lengths are equal because: