题干

已知半径R的球的球面上有三个点,其中任意两点间的球面距离都等于πR
3
,且经过这三个点的小圆周长为4π,则R=(  )

A:43

B:23

C:2

D:3

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答案(点此获取答案解析)

B

同类题3

2015年政府工作报告指出,要进一步推进长江经济带建设。阅读材料,完成下列要求。

材料一:长江经济带覆盖上海、江苏、湖北等11个省市,贯穿东、中、西三大地带,交汇京九、皖赣等南北铁路干线;具有丰富的淡水资源、矿产资源、旅游资源及农业生物资源;汇集了我国钢铁、汽车、电子、石化等现代工业的精华,集中了大批高科技的工业行业和特大型企业。专家预测,长江经济带在未来15年经济增长速度将超过全国经济的平均增速,到2020年前后长江经济带的经济总量将达到全国的50%。

材料二:为积极推动长江经济带融合发展,某省已初步拟定实施长江经济带的指导意见和规划,深入推进五项重点工程项目建设:实施枢纽建设工程,打造包括航运、铁路在内的综合立体大交通体系;实施产业转型升级工程,重点加强创新能力建设;实施大开放工程,营造对外开放新格局,推进长江中游城市群、跨江跨区合作;实施生态文明建设工程,建设长江中游生态文明示范带,发展循环经济,实现绿色增长;实施沿江新型城镇化推进工程,建设新型城市连绵带。

材料三:自我国提出建设长江经济带的战略构想以来,各地区多措并举,在拉动基础设施一体化、新的产业发展、就业等方面取得众多成就。但是,我们也应看到,各地“多头管理”,关联性不足,缺少统一协调;部分省市还在保留带有保护本地产品销售的政策规定,通过行政手段搞不公平竞争;一些地方对原有经济园区“开而不发”,当前又借长江经济带建设之名扎堆规划各类新园区;产业转移过程中经济发展与环境保护失衡,环境信息不透明……这些因素在一定程度上制约了长江经济带的协调发展,对沿线各地政府提出了新的挑战。

同类题5

阅读理解

    A drug that is used to treat serious bleeding could save thousands of lives of mothers giving birth. A world test of the drug found it reduced (降低) the risk of bleeding deaths during childbirth by nearly one third. The study included 20,000 women in 21 countries, mainly in Africa and Asia. The test was carried out by London School of Hygiene and Tropical Medicine. The drug is called tranexamic acid (凝血酸). It is low-cost and researchers said it does not cause serious side effects (副作用) for mothers or babies.

    The drug is used to treat mothers for serious bleeding during childbirth. Postpartum hemorrhage (产后出血) is the main cause of mothers' death around the world, according to the World Health Organization.

    Haleema Shakur is the project director for the test. She said though medical condition is improved in many countries, serious bleeding after childbirth remains a big problem in some parts of the world. “It's one of the biggest killers of mothers. In Africa and Asia, about 10% of women will end up with serious bleeding.” The drug works after a mother gives birth.

    Shakur said the best results were reported when the drug was given to women as soon as possible after childbirth. “The earlier you give it — within the first three hours after giving birth — the better the result is.”

    The next step will be to provide training for doctors and nurses on how to use it and then to find where the drug is needed. During the test, women were given the drug in a hospital. But researchers are looking for easier ways to use the drug so it can be more widely used in small clinics and the countryside.