Which of the following is $NOT$ a characteristic of a plasmid?

About gene gun method:
$I.$ This method is also known as biolistic technique.
$II.$ In this method,cells are bombarded with high-velocity micro-particles of gold or tungsten coated with $DNA$ in plants.
$III.$ Important crop plants like maize,rice,and wheat have now been transformed by this method.
Which of the statements given above are correct?

Which of the following hydrolases cleaves internal phosphodiester bonds in a polynucleotide chain?

Which of the following has popularized the $PCR$ (polymerase chain reaction)?

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

What is agarose?