单选题 Through modern medical science and technology, the average human life has been prolonged to 72 years.
【正确答案】 B
【答案解析】[解析] 句意：凭借现代医疗科技，人类平均寿命已经延长至72年。prolong延长。precipitate加速，促成。stretch拉长，伸展；延续。change改变。turn转变。