The correct option is A C6H5CH2Cl
All the molecules undergoing SN1 reaction shows racemisation as there is formation of 2 types of product in equal amount. Out of all these 4 alkyl halides , C6H5CH2Cl i.e benzylic chloride has the strongest tendency to undergo SN1 here thus leading to formation of racemic mixture as it contains benzylic carbocation which is most stable.