Answer: I think it‘s 1, it just makes more sense. Sorry if I am wrong but hope this helps anyone.
D is the answer because carbondioxide and oxygen are both needed for plants or green plants to survive.
I hope it helped
Climate effects and human impacts, that is, nutrient enrichment, simultaneously drive spatial biodiversity patterns. However, there is little consensus about their independent effects on biodiversity. ... Species turnover rates caused by nutrients do not increase toward higher temperatures