Which organism was used as experimental material to study $DNA$ replication?

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:

During $DNA$ replication,one strand is formed continuously and the second strand is formed discontinuously because:

Select the incorrect option from the following.

The replication fork is a .......

Self-replication occurs in