Purines found both in DNA and RNA are

Concept: 
-DNA and RNA are the polymers of nucleotides.
-A nucleotide has 3 components: a nitrogenous base ( A, T, G, C), a pentose sugar, and a phosphate group.
-There is a total of five nucleotides, 2 purines (adenine and guanine) and 3 pyrimidines (cytosine, thymine, and uracil).
-In both DNA and RNA, purines are the same but pyrimidines are different.
-In DNA, cytosine and thymine pyrimidines are present while in RNA cytosine and uracil pyrimidines are present

✅ Explanation:
Option 1: Adenine and thymine
-Adenine is a purine but thymine is a pyrimidine.
Option 2: Adenine and guanine– CORRECT
-Adenine and guanine are both purines and we know that purines are the same in both DNA and RNA.
Option 3:Guanine and cytosine
-Guanine is a purine but cytosine is a pyrimidine.
Option 4: Cytosine and thymine

✏️Cytosine and thymine pyrimidines are present in DNA not in RNA.🔴Additional Information::

• Nucleotide:

• Each nucleotide has the following three components:

✏️Sugar:
-A pentose sugar (five-carbon compound and pentagonal ring structure) is called deoxyribose (C5H10O4) or ribose (C5H10O5).

✏️Phosphate group:
-It is derived from phosphoric acid (H3PO4) and helps to link the nucleotides during strand formation.
-The phosphate group is attached to the 5th carbon of the sugar molecule by means of a sugar-phosphate bond.

✏️Nitrogen bases:
-These are cyclic compounds that show the presence of carbon, hydrogen, oxygen, and nitrogen atoms.
-The bases are named adenine (A), thymine (T), cytosine (C), guanine (G), and uracil (U).
-These are further divided into two groups – Purines and Pyrimidines.
-Purines are double-ring compounds (5 carbon atoms and 4 nitrogen atoms).
-Purines include: Adenine (A) and Guanine (G)
-Pyrimidines are single-ring compounds (4 carbon atoms and 2 nitrogen atoms).
-Pyrimidines include: Cytosine (C), Thymine (T), and Uracil (U)