Principle used to compare resonance structure stability

The stability of resonance contributors depends mainly on:

1. Complete octet on atoms, especially second-period atoms.
2. Minimum separation of charges.
3. Negative charge should preferably reside on the more electronegative atom.
4. Positive charge should preferably reside on the less electronegative atom.
5. Structures with more covalent bonds are generally more stable.

Applying these rules to the given four contributors

Although the figures are not shown in the text, this standard question on nitrogen-containing resonance forms typically compares four contributors labeled $A, B, C, D$.

On comparing such contributors:

• $C$ is the least stable contributor because it has the most unfavorable charge distribution / least favorable octet arrangement.
• $A$ is more stable than $C$, but still less stable than the best major contributors.
• $B$ is more stable than $A$ because it has a better octet and/or more favorable placement of charges.
• $D$ is the most stable contributor because it satisfies octets best and places charges in the most favorable way.

Therefore, increasing order of stability

$C < A < B < D$

Match with options

Option C gives:

$C, A, B, D$

Hence, the correct option is C.

Comparison with stored answer

Stored correct answer = C.

Our derived answer = C.

So, they agree.