Question

what is the part labeled b called?

nucleotide
nitrogen base
phosphate group
5 - carbon sugar

Explanation:

A nucleotide is composed of three parts: a phosphate group (A in the diagram), a nitrogen - containing base (C in the diagram), and a 5 - carbon sugar (B in the diagram). The 5 - carbon sugar is a pentose sugar (in the case of DNA, it is deoxyribose; in RNA, it is ribose). The phosphate group is the negatively charged part, the nitrogen base is heterocyclic (like adenine, guanine, cytosine, thymine in DNA or uracil in RNA), and the 5 - carbon sugar forms the central part of the nucleotide's structure to which the other two components are attached.

Answer:

5 - carbon sugar