The correct option is D A and B
A reducing sugar is of acting as a reducing agent because it has a free aldehyde group or a free ketone group.
All monosaccharides are reducing sugars, along with some disaccharides, some oligosaccharides, and some polysaccharides.
The monosaccharides can be divided into two groups: the aldoses, which have an aldehyde group, and the ketoses, which have a ketone group. Ketoses must first tautomerize to aldoses before they can act as reducing sugars.
The common dietary monosaccharides galactose, glucose and fructose are all reducing sugars.