Once 国语站 题库 2.69W 大中小设置文字大小 问题详情: Once ______ as an economic resource, the River Thames was polluted, ______ disease and death everywhere.A. known; caused B. knowing; to cause C. known; causing D. knowing; causing【回答】C知识点:非谓语动词题型:选择题 TAG标签:#