题干
------She looks very happy. She ______ have passed the exam.
------I guess so. It’s not difficult after all.
------I guess so. It’s not difficult after all.
A：should
B：could
C：must
D：might
答案(点此获取答案解析）
C
和双曲线
有相同的焦点
是椭圆与双曲线的一个交点，则
等于： （ ）