A:and
B:so
C:but
D:or
The factory ______ its waste into the river, but now it deals with the waste in a new way.
如图为二次函数y=ax2+bx+c(a≠0)的图象,则下列说法:①a>0 ②2a+b=0 ③a+b+c>0 ④当﹣1<x<3时,y>0其中正确的个数为( )