Lines 22-26 tell us that trees do produce oxygen by photosynthesis but when they die, the decomposition process consumes as much oxygen as the tree produced, resulting in zero net amount of oxygen. (E) is the most analogous because it talks about two separate processes that taken together result in net-zero change in the amount of water on the ground, whether in the form of rain or snow. The rest of the answer choices fail to describe two proportionate but opposite forces/ processes that counteract each other.