These three important bio-molecules are similar in that they have at least one carbon-based sugar.
Explanation;
Deoxyribonucleic (DNA) is a molecule that carries genetic information in an organisms, it contains a deoxyribose sugar which is a five sugar molecule that helps form the phosphate backbone of DNA molecules.
RNA (ribonucleic acid) on the other hand, contains ribose sugar, which is also a five carbon sugar, which is a sugar made in the body from glucose.
Starch is a polysaccharide which is formed when glucose molecules join together via the glycosidic bonds