Which of the Following Measurements Would Be Most Helpful in Understanding

Which of the following measurements would be most helpful in understanding the structure of an ecological community?
I. determining how many species are present overall
II. determining which particular species are present
III.determining the kinds of interactions that occur among individuals of the same species
IV.determining the abundance of resources available for one species

A) only I and II
B) only II and IV
C) only I, II, and III
D) I, II, III, and IV