L-isomer of a compound ' A ' ( C_4 H_8 O_4) gives a positive test with [ Ag ( NH_3)_2]^+. Treatment of 'A' with acetic anhydride yields triacetate…

L-isomer of a compound ' A ' $\displaystyle \left(\mathrm{C}_4 \mathrm{H}_8 \mathrm{O}_4\right)$ gives a positive test with $\displaystyle \left[\mathrm{Ag}\left(\mathrm{NH}_3\right)_2\right]^{+}$. Treatment of 'A' with acetic anhydride yields triacetate derivative. Compound 'A' produces an optically active compound (B) and an optically inactive compound (C) on treatment with bromine water and $\displaystyle \mathrm{HNO}_3$ respectively. Compound $\displaystyle (\mathrm{A})$ is :