题目

椭圆的短轴长是2，长轴是短轴的2倍，则椭圆中心到其准线的距离是…(    )A.             B.            C.             D. 答案：提示：依题意，b=1，a=2,∴c=,则椭圆中心到其准线的距离为=.答案：D--There __________ a big lake near my house. But it’s gone now.--That’s too bad.A. used to have B. used to beC. will have D. will be