Dahlia mosaic virus has which of the following as its genetic material?

$A$: Viruses are considered as a link between living and non-living organisms.
$R$: Viruses behave as inert,non-living particles in a free state,while they exhibit active,living behavior inside a host cell.

$A$ scientist $X$ demonstrated that the extract of infected plants of $Y$ could cause infection in healthy plants and called the fluid as "Contagium vivum fluidum". Identify $X$ and $Y$.

What are the algal components of a lichen called?

Which structure do lichens use for sexual reproduction?

In the given figure,what does the part labeled as $A$ represent?