Answer;
-Hydroxyl groups.
-They have multiple hydroxyl groups.
Step-by-step explanation;
-Monosaccharides are the simplest form of sugars found in common food items such as honey, cane sugar, fruits. They are the building blocks of other carbohydrates (disaccharides and polysaccharides).
-The are formed by three elements and three elements only: Carbon (C), Hydrogen (H) and Oxygen (O). Monosaccharides have two broad classifications on the basis of the functional group present in them, that is; aldose (contains aldehyde group) and ketose (contains a keto group).
-Monosaccharides contain multiple hydroxyl groups, and are responsible for the hydrophillic property of monosaccharides allowing them to dissolve in water easily.