The sugar unit present in the nucleotides of RNA is

The sugar is D− ribose in the group of nucleic acids known as ribonucleic acis (RNA), and D−2 dexoyribose in the group known as dexyribonucleic acids (DNA). The profix 2- dexoy simply indicates the lack of an −OH group at the 2-position. The sugar units are in the furanose form, and are joined to phosphate through the C−3 and C−5 hydroxyl groups. 
Thus, the ribose sugar that takes part in the formation of RNA is actually β−D ribofuranose while the sugar unit present in is actually β−D ribofuranose while the sugar unit present in a DNA molecule is actully 2 - deoxy - α−D- ribofuranose