Which enzyme joins the broken strands of $DNA$?

The gene of interest was cloned at the $Sal I$ site in $pBR322$. The recombinant plasmid will exhibit susceptibility to:

The given figure is the diagrammatic representation of the $E. coli$ vector $pBR322$. Which one of the given options correctly identifies its certain component$(s)$?

Which of the following has the ability to replicate independently within a bacterial cell?

Recombinant $DNA$ can be obtained by cutting pro-$DNA$ using:

$pBR-322$ is frequently used as a cloning vector. What is it?