题干
9. –You should have apologized to them for not ______ at the party.
--I ________ but they didn’t forgive me anyway.
A：coming up; did
B：turning up; did
C：showing up; should have
D：appearing; should
答案(点此获取答案解析）
B
所截弦的中点的轨迹为C,则曲线C与直线