题干
--- Liu Yi, do you miss your parents? I hear that you go back home once every month.
---Of course. You know this is the first time I_____ in the dormitory at school, far away from my hometown, Luoyang.
---Of course. You know this is the first time I_____ in the dormitory at school, far away from my hometown, Luoyang.
A：have stayed
B：stayed
C：stay
D：am staying
答案(点此获取答案解析）
A
（t为参数)点M、N在椭圆上，对应参数分别为 
， 
，则直线MN的斜率为