In the reaction of benzene with an electrophile ${\mathrm{E}}^{+}$, the structure of the intermediate $\sigma$-complex can be represented as __________

The major product of the following reaction is

In the following reaction sequence

$\mathrm{X}$ and $\mathrm{Y}$ are, respectively

Reaction of aniline with ${\mathrm{NaNO}}_2+$ dilute $\mathrm{HCl}$ at $0°\mathrm{C}$ followed by reaction with $\mathrm{CuCN}$ yields.

In the reaction

$\mathrm{x}, \mathrm{y} \text{and} \mathrm{z}$ are

$\mathrm{X}, \mathrm{Y}$ and $\mathrm{Z}$ in the following reaction sequence are

Among the following.

I 

II 

III 

IV 

V 

The antiaromatic compounds are