看图,读一读,选择句子补全对话。
Lily: Good afternoon, Mum. I'm home.
Mum: ____ How are you today?
Lily:____ It's very hot today.
Mum: Have a pear, Lily.
Lily: ____
Mum: Taste it. ____
Lily: It's sweet and juicy.
Mum: ____
Lily: Yes, I do.
①二次三项式ax2+bx+c的最大值为4;
②4a+2b+c<0;
③一元二次方程ax2+bx+c=1的两根之和为﹣1;
④使y≤3成立的x的取值范围是x≥0.
其中正确的个数有( )