题目

已知椭圆的长轴长是短轴长的倍，则该椭圆的离心率为（ ）A. B. C. D. 答案：【答案】C【解析】由题意，，再用平方关系算得，最后利用椭圆离心率公式可求出椭圆的离心率．∵椭圆的长轴长是短轴长的倍，∴，得，又∵a2＝b2+c2，∴2b2＝b2+c2，可得，因此椭圆的离心率为e．故选：C． The cousins are alike in age, but _____ they are as different as day and night. A. anyhow                   B. besides                    C. otherwise                 D. moreover