An aldotetrose G is reduced by sodium borohydride (NaBH4) to produce an optically active alditol, H. Elongation of G, via Kiliani-Fischer synthesis, produces I, which undergoes oxidation by nitric acid to an optically active diacid, J. Aldotetrose G has the L configuration.

Draw the Fischer projections of compounds G, H, I and J and explain your answer.