Which of the following is used in genetic engineering?

Which of the following methods are used for the analysis of Restriction Fragment Length Polymorphism $(RFLP)$?
$1$. Electrophoresis
$2$. Electroporation
$3$. Methylation
$4$. Restriction digestion

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.

Genetic engineering is possible because:

The most commonly used enzyme for polymerase chain reaction is

The key tools required for the recombinant $DNA$ technology are:
$I.$ Enzymes
$II.$ $RNA$ primer
$III.$ $DNA$ probe
$IV.$ Vectors
$V.$ Host organisms
Select the correct option.