Which of the following techniques is based on the principle of antigen-antibody interaction?

Humulin is

$P -$ Methods capable of early diagnosis
$Q -$ Methods not capable of early diagnosis
$I - rDNA$ technology $\quad II -$ Serum analysis $\quad III - PCR$
$IV -$ Urine analysis $\quad V - ELISA$
Select the correct option for $P$ and $Q$.
$P\quad\quad Q$

Which of the following techniques serves the purpose of early diagnosis of $AIDS$,cancer,etc?
$I$. Polymerase chain reaction
$II$. Recombinant $DNA$ technology
$III$. Enzyme-linked immunosorbent assay
Choose the correct option.

Which one of the following vectors is used to replace the defective gene in gene therapy?

An example of gene therapy is .......