Answer the following question given this paragraph: 

It was known that DNA is composed of nucleotides , each of which contains a nitrogen-containing base, a five-carbon sugar (deoxyribose), and a phosphate group. In these nucleotides, there is one of the four possible bases: adenine (A), guanine (G), cytosine (C), or thymine (T) ( Figure below ). Adenine and guanine are purine bases, and cytosine and thymine are pyrimidine bases.


Q: What does the base of a nucleotide within dna consist of?

 Choices:

- ribosomes

- protein

- hydrogen

- nitrogen

A:
nitrogen
