❓ 質問 According to the passage, what is the primary reason the starfish *Pisaster ochraceus* is considered a keystone species?
- A. A. It is the most numerous species in the intertidal zone.
- B. B. It preys on sea urchins, which would otherwise destroy kelp forests.
- C. C. Its removal leads to a decrease in species diversity due to mussel dominance.
- D. D. It creates physical structures that provide habitats for other organisms.