题干
-Jeff seems unhappy. What's the matter?
-He got his bike lost this afternoon. Let's go to __________ him __________.
A：cheer, up
B：make, up
C：set; up
答案(点此获取答案解析）
A
是定义在
上的奇函数，且
是偶函数，当
时，
，则
=【 】
