निम्न में 'A','B','C', 'D' पहचानो
`{:(C_(2) H _(5) +KOH overset(-k Br) to A overset(CaOCl_(2)) underset(-CaCl_(2)) to B overset(Ag) underset(-6A gCl)toC overset(Hg ^(++)) underset(H^(+))to D),(" "-(HCOO)_(2) Ca " "+H_(2)O), (" "-H_(2)O):}`