The electrophile used in the sulfonation of benzene is..........

Which of the following is most reactive toward electrophilic aromatic substitution reaction?

Friedel-Crafts reaction using $MeCl$ and anhydrous $AlCl_3$ will take place most efficiently with

$ArH + R - C(=O) - Cl \xrightarrow{\text{Lewis acid}} Ar - C(=O) - R + HCl$ is an example of

$CH_3-CH_2-CH_2-Cl$ $\xrightarrow{Na, \text{Dry ether}} P$ $\xrightarrow[V_2O_5, Al_2O_3]{\Delta} Q$. $Q$ is

Deduce the structure of $(A)$.
$(A) \ C_{8}H_{10}$ $\xrightarrow{KMnO_{4}} (B) \ C_{8}H_{6}O_{4}$ $\xrightarrow[Fe]{Br_{2}} C_{8}H_{5}BrO_{4} (C)$ (one-product only)