Which metals are used in a gene gun for the insertion of alien $DNA$ into a competent host?

The first restriction endonuclease was isolated from which of the following?

Given below are two statements :-
Statement-$I$ : Restriction endonucleases recognize specific sequences to cut $\text{DNA}$ known as selectable nucleotide sequences.
Statement-$II$ : Restriction endonucleases cut the $\text{DNA}$ strand a little away from the centre of the palindromic site.
In the light of the above statements,choose the most appropriate answer from the options given below :-

$A$ plasmid:

Which of the following is used in recombinant $DNA$ technology?

What is the function of restriction endonucleases?