The correct option is B 1-butanol
Alkyl halides give alcohols with aq. KOH, which is a substitution reaction. Thus 1-Chlorobutane on reaction with aq. KOH gives 1-butanol. Hence correct option is (b).
H3C−H2C−H2C−CH2Claq.KOH−−−−−→CH3−CH2−CH2−CH2OH1-butanol