In lichens,the male and female reproductive structures are produced by which of the following?

The infectious agents made up of $RNA$ only are

$A.$ Viroids are the pathogens responsible for Parkinson's disease in humans.
$R.$ Viroids are smaller in size than viruses.

$A$ virus can be considered a living organism because it

$T. O.$ Diener discovered a new infectious agent that was smaller than viruses and has the following characteristics:
$(i)$ It causes potato spindle tuber disease.
$(ii)$ It has free $RNA$.
$(iii)$ The molecular weight of $RNA$ is low.
Identify the infectious agent.

What are the fungal components of a lichen called?