Which from the following nitrogen bases of nucleic acids is derived from purine?

Two nucleotides are joined together by a linkage known as:

. . . . . . nucleotide is not present in $RNA$.

The pyrimidine bases present in $DNA$ are

Given below are two statements:
Assertion $(A)$: Hydrolysis of $DNA$ does not form equal number of $A$ and $T$; $G$ and $C$.
Reason $(R)$: In $DNA$,adenine forms hydrogen bonds with thymine and cytosine forms hydrogen bonds with guanine.
The correct answer is:

$RNA$ and $DNA$ are chiral molecules. Their chirality is due to the presence of: