A:①②
B:①③
C:②④
D:③④
It took this small village five years to develop into a small town.
已知关于x的方程x2+(1+a)x+1+a+b=0(a,b∈R)的两根分别为x1、x2,且0<x1<1<x2,则ba的取值范围是( )