Question

Below given structure is of:

• A. Vitamin C
• B. Thymine
• C. Thymosin
• D. Cytosine

Hint:

Cytosine has “one keto and one amino” group on its single ring.

Answer 1

The Correct Option is D

Step 1: Concept
Nitrogenous bases are building blocks of nucleic acids, classified as purines (double ring) or pyrimidines (single ring).

Step 2: Meaning
Each base has a specific molecular arrangement of atoms.

Step 3: Analysis
The structure shown is a single-ringed pyrimidine with an amino group ($-\mathrm{NH_{2}}$) at position 4 and a keto group at position 2. This is the chemical signature of Cytosine. Thymine has two keto groups and a methyl group.

Step 4: Conclusion
The molecular structure represents Cytosine.

Final Answer: (D)