Which antibiotic resistance is naturally found in $E. coli$?

In the nomenclature of the enzyme $Restriction$ $Endonuclease$,what does the Roman numeral indicate?

Which enzyme is used for the separation of genetic material?

$DNA$ ligase is an enzyme that .......

$A$ - Restriction endonucleases are also called 'molecular scissors'.
$R$ - When fragments generated by restriction endonucleases are mixed,they join together due to their sticky ends.

In vector $\text{pBR-322}$,the $\text{Rop}$ codes for the $:-$