题干
. --- He has to finish the experiment today. He must be in the lab,________?
---That s quite possible.
A：mustn't he
B：won't he
C：doesn't he
D：isn't he
答案(点此获取答案解析）
D
为直径两端点的圆，恰好过短轴的两顶点，则此椭圆的离心率
等于 （ ）