Which of the following is the most unlikely representation of resonance structures of $\mathrm{p}-$nitrophenoxide?

The correct order of stability of various resonating structures of $1$$-$methoxy$-1,3-$butadiene is:

(i) ${\mathrm{CH}}_3-\mathrm{O}-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}={\mathrm{CH}}_2$

(ii) ${\mathrm{CH}}_3-\stackrel{+}{\mathrm{O}}=\mathrm{CH}-\stackrel{-}{\mathrm{C}}\mathrm{H}-\mathrm{CH}={\mathrm{CH}}_2$

(iii) ${\mathrm{CH}}_3-\stackrel{+}{\mathrm{O}}=\mathrm{CH}-\mathrm{CH}=\mathrm{CH}-\stackrel{-}{\mathrm{C}}{\mathrm{H}}_2$

(a) $\mathrm{H}-\stackrel{+}{\mathrm{C}}=\stackrel{..}{\mathrm{O}}:\leftrightarrow \mathrm{H}-\mathrm{C}\equiv \stackrel{+}{\mathrm{O}}:$

(b) $\stackrel{-}{\mathrm{C}}{\mathrm{H}}_2-\stackrel{+}{\mathrm{N}}\equiv \stackrel{..}{\mathrm{N}}\leftrightarrow {\mathrm{CH}}_2=\stackrel{+}{\mathrm{N}}=\stackrel{-}{\mathrm{N}}$

(c) ${\mathrm{CH}}_3-\stackrel{+}{\mathrm{C}}\mathrm{H}-\underset{..}{\overset{..}{\mathrm{O}}}\mathrm{H}\leftrightarrow {\mathrm{CH}}_3-\mathrm{CH}=\underset{..}{\overset{+}{\mathrm{O}}}\mathrm{H}$

In which of the above pairs of resonance contributors, the structure on the right is an important contributor?

I 

II 

III 

IV 

The correct order of $\mathrm{C}-\mathrm{N}$ bond length in the above compound is:

Which of the above hydrogen is most acidic?

The correct order of $\mathrm{C}-\mathrm{Cl}$ bond length in the given molecules is:

I 

II 

III 

Which of the following is the strongest base?