chem aits doubt(probably basic af)

X’ is an aliphatic monocarboxylic acid. It is the simplest acid which can form only one alpha()-chloroproduct(Y), upon treatment with Cl2 in presence of red phosphorus(H.V.Z reaction). What is the molar mass of X in g mol–1 unit?

why is the answer not ethanoic acid? according to answer key it is (ch3)2chcooh....

is it cause more than one chlorine gets attached?