B. The area's climate
Specific plants need specific climate conditions in order to survive. The other answer choices have little to no impact on the growth of plants.
I think BO or B, but BO has more chance.
D. A struggle for existence is apparent.
If a struggle for existence is apparent, natural selection occurs because all of the weak/unfit/unadapted ones die.
The results from the research suggest that a person who experiences auditory hallucinations that are localized in the expressive area of the brain is actually listening to his or her own thoughts. Since the problem is in the expressive area, this shows that the patient is only listening to the ideas his brain is already producing.