❓ 题目 According to the passage, what is the primary reason the starfish Pisaster ochraceus is considered a keystone species?
- A. A. It is the most abundant organism in the intertidal zone.
- B. B. Its predation on mussels prevents mussels from dominating and allows other species to coexist.
- C. C. It directly provides food for a wide variety of other organisms.
- D. D. It is an ecosystem engineer that modifies the physical habitat.