If there are two pathogenic viruses, one with $DNA$ and other with $RNA$, which would mutate faster ? And Why ?

After infection by pathogens dead cells, dead pathogens and liquid form the

Which one of the following causes plague

Identify the molecules $(A)$ and $(B)$ shown below and select the right option giving their source and use.

Molecule             $\to $         Source                  $\to $                Uses

Who among the following established the scientific basis of vaccination?