The primary difficulty is the fact that we do not know all of the organisms that currently exist in the world along with those that existed in the past.
I think tracheae which is B not sure tho
Usually if they have chloroplasts, they’re autotrophic. If they don’t have chloroplasts then they’re autotrophic, although members of Excavata like euglenozoans can be mixotrophic
Explanation:
you just need to know that :
population density = no of ( what is asked) / land area.