Among the given sets,which represents the resonating structures?

• A
  $H-C \equiv N^{+}-O^{-}$ and $H-O^{-}-C \equiv N$
• B
  $H-O^{+}=C=N^{-}$ and $H-O-C \equiv N$
• C
  $H-C \equiv N^{+}-O^{-}$ and $H-C(=O)-N:$
• D
  $H-O^{-}-C \equiv N$ and $H-N=C=O$