这个数可能是____？

设函数$f\left(x\right)=x^3-4x+a\left(0<a<2\right)$有三个零点$x_1,x_2,x_3$，且$x_1<x_2<x_3$则下列结论正确的是（  ）

It's important for us to be healthy. But how can we keep healthy? First,you should eat fruit and vegetables three or four times a week. Then eat some tofu every day because it's good for people, both the young and the old. Milk is also necessary(必要的），especially for women. So you should have milk twice a day. It can help you to be strong. Next, doing more exercise is better. You can do morning exercises or evening exercises. After supper you should take a walk.