题干
—You must get a high income by doing that kind of job.
—Oh，my income's rather variable，but I earn 100 yuan a day________.
A：on average
B：in common
C：in all
D：on the whole
答案(点此获取答案解析）
A
，若
＞0，
＞0，则函数
在区间
内（ ）