The polio vaccine was developed by:

Who discovered interferons?

The percentage of the population suffering from serious mental illness is: (in $\%$)

Sprinkling oil over ponds would control malaria because

What measures can be taken to maintain public health against water-borne diseases?

$A$: It is considered advantageous to give the polio vaccine orally.
$R$: It prevents reinfection by causing intestinal immunity.