Study the given figure carefully and select the correct statements regarding this

$I.$ It represents typical agarose gel electrophoresis which showing differential migration of $DNA$ fragments

$II.$ Lane $1$ contains undigested $DNA$ fragments

$III.$ Lanes $2$ to $4$ contains digested $DNA$ fragment

$IV.$ Smallest $DNA$ bands are present at ( $A$ ) position and largest $DNA$ bands are present at ( $B$ ) position

In recombinant $DNA$ technique, the term vactorrefers to a

Identify the part $A$ and $B$ from the given figure :

Ligases catalyse the formation of bonds between

Restriction enzymes are also called