A problem that confounds attempts to organize the entire living world for study?

A problem that confounds attempts to organize the entire living world for study is the need of evolutionists to bring the entire diversity of living things ultimately into.

In biology, living things can all be classified in accordance with other living things that share a specified set of common characteristics. A major challenge to the process of classification is that, in evolution, that this involves the need to classify all living things. The challenges being that there are many species on planet earth that once existed and are now extinct (i.e. they cannot currently be studied in living form) and that there may be species that do exist that have yet to be discovered and therefore cannot be classified. Finally, due to the sheer number of species on earth, it will literally take hundreds of years for scientists to classify all species.

the answer is c) an oak tree

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.