Which of the following acts as a pollution indicator?

An example of a plant virus is -

Enzymes are absent in

Viruses are known as:

Statement $X$: Lichens are composed of two main components. Statement $Y$: In lichens,the phycobiont is the heterotrophic component and the mycobiont is the autotrophic component.

Viruses are considered as a link between living and non-living organisms because