函数y=x2-4x+6的值域为______．
函数y=x2-4x+6=（x-2）2+2≥2，
故y≥2，
函数的值域是：[2，+∞）．
封闭的火区，只有经取样化验证实火已熄灭后，方可启封或注销。其中4项指标之一的一氧化碳浓度在（）以下。
Alice in Wonder land is a fantastic movie. It’s about ().
A. how did Alice end the Red Queen’s reign of terror(恐怖统治)
B. what did Alice end the Red Queen’s reign of terror
C. how Alice ended the Red Queen’s reign of terror
D. what Alice ended the Red Queen’s reign of terror
