Toluene on oxidation with dilute $HNO_3$ and alkaline $KMnO_4$ gives:

Which of the following compounds undergoes sulfonation most easily?

Product $(Y)$ of the above reaction is

The best reagent for nuclear iodination of aromatic compounds is:

Consider the following compounds/species:
The number of compounds/species which obey $H$ückel's rule is $..........$

Cyclic hydrocarbon molecule $A$ has all the carbon and hydrogen atoms in a single plane. All the carbon-carbon bonds are of the same length and are less than $1.54 \ \mathring{A}$ but more than $1.34 \ \mathring{A}$. The $C-C-C$ bond angle will be: