题干
Mr. Li devoted all his life English. Now he retired.
A：to teach
B：to teaching
C：to be taught
D：to have being taught
答案(点此获取答案解析）
B
给出函数f (x)＝2－x－x2，若对于任意x∈［0，＋∞)，恒有fK(x)＝f(x)，则（ ）
