❓ 题目 According to the passage, which of the following best describes the main idea of the keystone species concept?
- A. A. Keystone species are always top predators whose removal causes biodiversity loss.
- B. B. Certain species have a disproportionately large impact on their ecosystem relative to their abundance.
- C. C. The concept was first proposed by Robert Paine based on experiments with beavers.
- D. D. Keystone species are defined by their high biomass and competitive dominance.