Five-carbon sugar (sugar) is called pentose sugar. Nucleic acids contain two types of pentose sugars. Ribose sugar and deoxyribose sugar.
(i) Ribose sugar: RNA molecule contains ribose sugar. It is a type of monosaccharide. Its 2nd carbon contains oxygen.
(ii) Deoxyribose sugar: DNA molecule contains deoxyribose sugar. It is a type of monosaccharide. Its 2nd carbon does not contain oxygen (deoxy = less of one oxygen) so named. That is why it is called 2-β-D deoxyribose sugar.