Which enzyme is required to obtain $DNA$ in its pure form from a cell?

Given below are four statements pertaining to the separation of $DNA$ fragments using gel electrophoresis. Identify the incorrect statements:
$(a)$ $DNA$ is a negatively charged molecule and so it is loaded on the gel towards the Anode terminal.
$(b)$ $DNA$ fragments travel along the surface of the gel,whose concentration does not affect the movement of $DNA$.
$(c)$ The smaller the size of the $DNA$ fragment,the larger is the distance it travels through it.
$(d)$ Pure $DNA$ can be visualized directly by exposing it to $UV$ radiation.
Choose the correct answer from the options given below:

Given below are two statements.
Statement $I$ - The isolated $DNA$ of donor organism is cleaved by suitable restriction endonuclease to form $DNA$ fragments with cohesive staggered or blunt ends.
Statement $II$ - The foreign $DNA$ or passenger $DNA$ can also be obtained directly from genomic or cDNA library.
In the light of above statements,select the correct option given below:

Study the given figure carefully and select the correct statements regarding this.
$I.$ It represents typical agarose gel electrophoresis showing differential migration of $DNA$ fragments.
$II.$ Lane $1$ contains undigested $DNA$ fragments.
$III.$ Lanes $2$ to $4$ contain digested $DNA$ fragments.
$IV.$ Smallest $DNA$ bands are present at $(A)$ position and largest $DNA$ bands are present at $(B)$ position.

What would happen when one grows a recombinant bacterium in a bioreactor but forgets to add antibiotic to the medium in which the recombinant is growing?

An artificial process of infecting cells with naked viral $DNA$ is: