Which metal is used in particle bombardment (biolistics) for gene transfer?

The plasmid used for the construction of the first artificial recombinant $DNA$ molecule was obtained from which microorganism?

Restriction enzymes may be used for:

Match the correct pair:

An antibiotic resistance gene in a vector usually helps in the selection of

Identify the desirable characteristics for a plasmid used in $rDNA$ technology from the following.
$A$. Ability to multiply and express outside the host in a bioreactor.
$B$. $A$ highly active promoter
$C$. $A$ site at which replication can be initiated
$D$. One or more identifiable marker genes
$E$. One or more unique restriction sites.