Viruses multiply

The symbiotic association between fungi and algae is called

Which of the following is a type of lichen based on its growth form?

$T. O.$ 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.

Which organisms are sensitive to $SO_2$ pollution?

Identify the organisms shown in the figures $A$,$B$,and $C$: