Answer:
The correct answer is - purine nitrogenous base (adenine).
Step-by-step explanation:
The base given in the diagram in the image has two rings attach with the pentose sugar which is attached to the phosphate, which means it is the diagram of nucleotide. In this nucleotide base can be either purine or pyrimidine.
Pyrimidines have a single ring structure, whereas purines have 2 ring structures. Adenine and guanine are purines with two ring structures whereas cytosine and thymine are pyrimidines as they have one ring structure. Adenine contains an amine group on C6, and a double bond between N1 and C6.