【简答题】The disease occurs most frequently rural areas.
【单选题】Which type of fever is usually occurs in purulent disease
【简答题】已知椭圆 的离心率为 ,直线 : 与以原点为圆心、以椭圆C 1 的短半轴长为半径的圆相切. (1)求椭圆C 1 的方程; (2)设椭圆C 1 的左焦点为F 1 ,右焦点F 2 ,直线l 1 过点F 1 且垂直于椭圆的长轴,动直线l 2 垂直l 1 于点P,线段PF 2 垂直平分线交l 2 于点M,求点M的轨迹C 2 的方程; (3)当P不在x轴上时,在曲线C 2 上是否存在两个不同点C、D关于PF...
【单选题】Match the disease with the definition._________:any disease or disorder that occurs during the course of (or because of) another disease.
【单选题】Heart disease occurs earlier in male than in female.
【简答题】已知椭圆C: x 2 a 2 + y 2 b 2 =1 (a>b>0)上的一动点P到右焦点的最短距离为 2 -1 ,且右焦点到右准线的距离等于短半轴的长. (Ⅰ) 求椭圆C的方程; (Ⅱ) 过点M(0, - 1 3 )的动直线l交椭圆C于A、B两点,试问:在坐标平面上是否存在一个定点T,使得无论l如何转动,以AB为直径的圆恒过定点T?若存在,求出点T的坐标;若不存在,请说明理由.
【单选题】____ occurs when a disease spreads quickly.
【简答题】_________,this kind of disease can do great harm to people there. A.Occurring where B.It occurs where it is C.Where does it occur D.Wherever it occurs