A:①②
B:①③
C:③④
D:②③
下图为我国主要糖料作物基地分布示意图。回答各小题。
____ ____,Paul !
I know this plan is far from perfect, but I just can't think of _______one.
若直线2ax-by+2=0(a>0,b>0)被圆x2+y2+2x-4y+1=0截得的弦长为4,则1a+1b 的最小值为( )