The Friedal – crafts alkylation reaction will give propyl phenyl ketone which on further Clemmenson’s reduction will give butyl benzene.
${\text{C}}_{\text{6}}{\text{H}}_{\text{6}}\text{+}{\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}\text{COCl}\stackrel{{\text{AlCl}}_{\text{3}}}{\to }{\text{C}}_{\text{6}}{\text{H}}_{\text{5}}{\text{COCH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}\stackrel{\text{Zn-Hg/HCl}}{\to }\underset{\text{Butylbenzene}}{{\text{C}}_{\text{6}}{\text{H}}_{\text{5}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}}$
Rest other will give 2-phenylbutane as in them rearrangement of carbocation is possible.