Resonating structures have different

$CH_2 = O \leftrightarrow \overset{\oplus}{C}H_2 - \overset{\ominus}{O} \leftrightarrow \overset{\ominus}{C}H_2 - \overset{\oplus}{O}$
Which of these structures is practically not a valid canonical structure for formaldehyde?

The correct bond order of the $B-F$ bond in the $BF_3$ molecule is:

Which of the following statements are true for the nitrate ion $(NO_3^-)$?
$(a)$ The coordination number of $N$ is $3$,and the structure is trigonal planar.
$(b)$ The formal charge on $N$ is $+1$.
$(c)$ The average formal charge on each $O$ atom is $-2/3$.
$(d)$ The average bond order of the $NO$ bond is $4/3$.
$(e)$ All $NO$ bond lengths are identical due to resonance.
Select the correct code:

What is the $O-O$ bond length in the ozone $(O_3)$ molecule (in $pm$)?

Which of the following compounds does not show resonance?