❓ 题目 According to the passage, why is the starfish Pisaster ochraceus considered a keystone species?
- A. A. It is the most abundant species in the rocky intertidal zone.
- B. B. Its removal caused a decline in mussel populations and increased diversity.
- C. C. It has a disproportionately large effect on community structure despite low abundance.
- D. D. It directly provides habitat for many other marine species.