Which of the following compounds will behave as reducing sugar in an aqueous KOH solution?

A reducing sugar is a carbohydrate that possesses a free hemiacetal or hemiketal group. In its cyclic form, the anomeric carbon is bonded to both an $$-OH$$ group and an $$-OR$$ (ring oxygen) group.

Compound A is inherently reducing, and not due to the aqueous solution of $$KOH$$

Acetals and Ketals (B & C): These are stable in basic solutions like aqueous $$KOH$$. The ring cannot open, so they remain non-reducing.

In the presence of $$KOH$$, the acetate group ($$-OCOCH_3$$) undergoes basic hydrolysis. This chemical reaction restores the free hemiketal group.

Hence, option (D) is the correct answer.