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.

• A
  $A, C, D$ and $E$ only
• B
  $B, C$ and $D$ only
• C
  $C, D$ and $E$ only
• D
  $B, C$ and $E$ only