The action of $AlCl_3$ in Friedel-Crafts reaction is

The major product $P$ formed in the following reaction is:

In which of the following reactions,$t$-butyl benzene is formed?
$1.$ Benzene $+ t$-butyl chloride $\xrightarrow{AlCl_3}$
$2.$ Benzene $+ (CH_3)_2C=CH_2 \xrightarrow{BF_3/HF}$
$3.$ Benzene $+ t$-butyl alcohol $\xrightarrow{H_2SO_4}$
$4.$ Benzene $+$ butanoyl chloride $\xrightarrow{AlCl_3}$ $\xrightarrow{Zn/Hg, HCl}$

Number of $\pi$ electrons present in naphthalene is :

Among the following,the aromatic compounds are:

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