--- Thank you!
--- ________
A:Don't say that!
B:That's right.
C:That's all right.
D:It is a welcome.
设函数f(x)=x2+2x,x<0-x2,x≥0,则f(1)=____ ,若f(f(a))≤3,则实数a的取值范围是____
《论语》云:管仲相(辅佐)桓公,霸诸侯,一匡天下。”这则材料反映的历史事件是( )
龙飞凤舞 ____ ____ ____ ____ ____