题干
It ______ a Saturday afternoon in May ______ Margaret could arrange for me to meet her elder sister.
A：was until; whe
B：was until; that
C：was not until; whe
D：was not until; that
答案(点此获取答案解析）
D
＝2，则
是奇函数，且当
时，
，则当
时，