How many resonance forms can be written for the nitrate ion,$(NO_3^-)$?

The $S-O$ and $P-O$ bond order in $SO_4^{2-}$ and $PO_4^{3-}$ are respectively:

The $C-C$ bond length in benzene is ...........

Draw the resonance structures for the following compounds. Show the electron shift using curved-arrow notation.
$(a)$ $C_{6}H_{5}OH$
$(b)$ $C_{6}H_{5}NO_{2}$
$(c)$ $CH_{3}CH=CH-CHO$
$(d)$ $C_{6}H_{5}CHO$
$(e)$ $C_{6}H_{5}CH_{2}^{+}$
$(f)$ $CH_{3}CH=CH-CH_{2}^{+}$

Compare the relative stability of the following resonating structures:
$(i)$ $CH_3-CH=C(CN)-COCH_3$
(ii) $CH_3-CH=C(CN)-C^+(O^-)CH_3$
(iii) $CH_3-C^+(H)-C(CN)=C(O^-)CH_3$
(Note: The structures are provided in the image.)

The most unlikely representation of resonance structures of $p-$nitrophenoxide ion is