题干
--- Is her sister a teacher or a student?
--- .
A：No, she's a teacher
B：No, she isn't a teacher
C：She's a student
D：Yes, she's a teacher
答案(点此获取答案解析）
C
--- Is her sister a teacher or a student?
--- .
A：No, she's a teacher
B：No, she isn't a teacher
C：She's a student
D：Yes, she's a teacher
在点
处的切线与直线
垂直，则
（ ）