Which of the following is a plasmid?

Which enzyme is responsible for joining two fragments of $DNA$?

An enzyme catalysing the removal of nucleotides from the ends of $DNA$ is:

Which of the following would not be used in preparing recombinant $DNA$?

How are antibiotics used in genetic engineering?

In the naming of restriction enzymes, the first letter is derived from $...A...$ name, the next two letters from the $...B...$, and the fourth letter from $...C...$ of $...D...$ where the enzymes are extracted.
$A$ to $D$ in the statement can be: