contributions to atmospheric oxygen from sources other than trees the ways in which industrialized nations use trees the root area of trees the bark mass of trees
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: While studying the relationship between number of trees and amount of atmospheric oxygen, which of the following would be most important to take into account?
Possibilities:
- contributions to atmospheric oxygen from sources other than trees
- the ways in which industrialized nations use trees
- the root area of trees
- the bark mass of trees

contributions to atmospheric oxygen from sources other than trees