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

Given below are two statements:
Statement $I:$
$DNA$ polymerases catalyse polymerisation only in one direction,that is $5^{\prime} \rightarrow 3^{\prime}$.
Statement $II:$
During replication of $DNA$,on one strand the replication is continuous while on the other strand it is discontinuous.
In the light of the above statements,choose the correct answer from the options given below:

$DNA$ replication requires:

Given below are two statements,one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R).$
Assertion $(A):$ $\text{DNA}$ replication occurs within a small opening of the $\text{DNA}$ helix,referred to as the replication fork.
Reason $(R):$ During transcription,the discontinuously synthesized fragments of $\text{DNA}$ are joined by the enzyme $\text{DNA}$ ligase.
In the light of the above statements,choose the most appropriate answer from the options given below:

Heavy $DNA$ is separated from normal $DNA$ based on which of the following?

$DNA$ polymerase helps in