The protein coat of a virus is called ...........

Viruses are $....$.

Write a short note on viruses.

Assertion $A$: Bacteriophages are bacteria-eating viruses.
Reason $R$: Bacterial viruses are obligate parasites in bacterial cells.
Which option is correct for Assertion $A$ and Reason $R$?

$A$: Viroids lack a protective protein coat called a capsid.
$R$: Viroids contain a short strand of $DNA$.

The polio virus is a ........