The correct option is B Pent-1-ene
Alkyl halide on reacting with alcoholic KOH undergo elimination via E2 mechanism.
n-Pentylbromide undergo 1, 2- elimination to form Pent-1-ene.
CH3CH2CH2CH2CH2Brn−Pentyl bromide Ethanolic KOH−−−−−−−−−→CH3CH2CH2CHPent−1−ene=CH2+KBr+H2O
Hence, (b) is the correct answer.