In which type of $DNA$ replication,out of the two newly formed molecules,one is purely new and the other is entirely old?

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:

Replication of $DNA$ occurs in which direction?

$DNA$ repairing is done by

During which process are Okazaki fragments formed?

Who used heavy nitrogen $N^{15}$ for proving the semiconservative way of $DNA$ replication?