A compound A of formula C3H6CI2 on reaction with alkali can give B of formula C3H6O or C of formula C3H4. B on oxidation gave a compound of the formula C3H6O2. C with dilute H2SO4 CONTAINING Hg2+ ion gave D of formula C3H6O, which with bromine and NaOH gave the sodium salt of C2H4O2. Then A is:
CH3CH2CHCl2
Since, B and D are different thus, B is CH3CH2CHO and so A is CH3CH2CHCI2.