Which one of the following causes crown gall disease?

Autonomously replicating circular extrachromosomal $\text{DNA}$ is called:

$A$ plasmid without a selectable marker was chosen as a vector for cloning a gene. How does this affect the experiment?

Which of the following is important in genetic engineering?

Which of the following enzymes cuts $DNA$ at specific sites?

$A$ : $Pst I$ generates single-stranded overhanging stretches in $DNA$ after digestion that facilitate ligation.
$R$ : These short extensions can form hydrogen bonds with their complementary counterparts,which are then sealed by $DNA$ ligase to form phosphodiester bonds.