$A$ $DNA$ fragment contains $12$ nucleotides. What is the ratio of purine and pyrimidine nitrogenous bases in it?

In the structure of $DNA$,which bond connects $Adenine$ with $Thymine$?

Which molecule is responsible for maintaining continuity between generations in living organisms?

What is the width (distance) between the two polynucleotide chains of $DNA$?

Identify the pair of nucleotides in $DNA$ that are linked by three hydrogen bonds.

$S$ Statement: $DNA$ is inherited by organisms produced by parents.
$R$ Reason: $DNA$ acts as a gene.
$(a)$ Both $S$ and $R$ are true,and $R$ is the correct explanation of $S$.
$(b)$ Both $S$ and $R$ are true,but $R$ is not the correct explanation of $S$.
$(c)$ $S$ is true and $R$ is false.
$(d)$ $S$ is false and $R$ is true.
$(e)$ Both $S$ and $R$ are false.