❓ 题目 According to the passage, what is the main reason the keystone species concept has been criticized?
- A. A. It overemphasizes the role of predators in ecosystems.
- B. B. It is difficult to predict which species are keystones before their removal.
- C. C. It fails to account for the importance of biomass in species interactions.
- D. D. It has only been applied to marine ecosystems like intertidal zones.