The textbook context defines carbohydrates as 'optically active polyhydroxy aldehydes or ketones or molecules which provide such units on hydrolysis' and classifies them into three groups: monosaccharides, disaccharides and polysaccharides. The Summary section explicitly states that 'Monosaccharides are held together by glycosidic linkages to form disaccharides or polysaccharides.' Additionally, the polysaccharides section describes monosaccharides as 'building blocks' of polysaccharide chains. For a 1-mark very short answer, students should mention that monosaccharides are a type of carbohydrate and that they serve as building blocks for larger carbohydrate molecules.