单选题 Because of ______ diversity, seven separate groupings or divisions of algae have been established by botanists.
【正确答案】 D
【答案解析】[解析] 句意：根据海藻的多样性，植物学家把它们分成7个不同的组别或分支。those是泛指，这里应该用their来特指seven separate groupings or divisions of algae。