题目

已知椭圆C:与椭圆有相同离心率,则椭圆C的方程可能是( )A.(m≠0)                    B.C.                                 D.以上都不可能 答案：解析：把方程写成,则a2=8m2,b2=4m2.∴c2=4m2.∴而椭圆的离心率为.答案:AThe light in his room is off．He ________ to sleep．A.may have goneB.can have goneC.could have goneD.must have gone