题干
--- Mum, could I play with my classmates for a while after I finish my homework?
--- _______. But you must come back before supper.
--- _______. But you must come back before supper.
A：Yes, you ca
B：Yes, you could
C：No, you can’t
D：No, you couldn’t
答案(点此获取答案解析）
A
（
且
）在
上的最大值与最小值之和为
，则
的值为 （ ）