According to paragraph 7, which of the following statements correctly characterizes the effect of sea stars on the ecosystem in which they are predators of bivalves? A. Bivalve population are kept low, allowing species that compete with bivalves to survive. B. The numbers of most species of bivalves are greatly reduced, leaving the bivalve species that is the strongest competitor to dominate among the survivors. C. Biological diversity begins to decrease because many bivalve species disappear. D. Sea stars dominate at first but then die off because of the depleted food supply.