A hydrocarbon A(molecular formula `C_(8)H_(10)`) on ozonolysis gives `B(C_(4)H_(6)O_(2))` only. Compound `C(C_(3)H_(5)Br)` on treatment with magnesium in dry ether gives (D) which on treatment with `CO_(2)` followed by acidification gives(B). Identify A, B, C and D.

An organic compound of molecula formula C_(6)H_(5)O"Na" is heated with CO_(2) at 400 K gives compound (A) of molecular formula C_(7)H_(5)O_(3)Na . Compound (A) on treating with HCl gives (B). B on further reactions wiith NaOH / CaO gives compound (C ) of molecular formula C_(6)H_(6)O which on treatment with nitrous acid at 200 K gives compound (D ). Identify (A), (B) , ( C) and (D) are explain the reactions.