Identify the enzymes that synthesize $DNA$ from $RNA$.

$A$: Kornberg enzyme is associated with the removal of primers and thymine dimers.
$R$: $DNA$ polymerase $I$ performs exonuclease activity in $5^{\prime} \rightarrow 3^{\prime}$ and $3^{\prime} \rightarrow 5^{\prime}$ directions.

The monomer of $DNA$ is deoxyribonucleotide. However,why is deoxyribonucleoside triphosphate used at the enzymatic site?

Synthesis of $DNA$ takes place by

$A$ $N^{15}-N^{15}$ $\text{DNA}$ molecule is continuously replicated in $N^{14}$ medium,then what is the percentage of heavy $\text{DNA}$ in the $4^{\text{th}}$ generation (in $\%$)?

Describe various enzymes involved in $DNA$ replication.