从方框中选择最佳选项完成对话，有两项多余。

A. It doesn't hurt any more.

B. When did it happen?

C. Was it serious?

D. How careless!

E. I'm sorry to hear that.

F. I hurt my finger when I was cutting a watermelon.

G. Do you know how to give first aid?

A: I had an accident yesterday.

B: ____ How did it happen?

A: ____

B: Bad luck! ____

A: No, but my finger hurt!

B: How do you feel now?

A: Much better. ____

B: You must be careful when you use a knife next time.

A: I will. My mother and father had warned me, but I didn't listen.

B: ____

A: Er, I won't cut watermelons with knives anymore.

B: Oh, don't be scared. It's OK if you're careful.

已知函数$\left\{\begin{array}{c}x+k\left(1-a^2\right),\left(x\ge 0\right)\\ x^2-4x+{\left(3-a\right)}^2,\left(x<0\right)\end{array}\right.$，其中a∈R．若对任意的非零实数x₁，存在唯一的非零实数x₂（x₁≠x₂），使得f（x₁）=f（x₂）成立，则k的取值范围为（　　）

在一个不透明的盒子里装有只有颜色不同的黑、白两种球共40个，小颖做摸球实验，她将盒子里面的球搅匀后从中随机摸出一个球记下颜色，再把它放回盒子中，不断重复上述过程，下表是实验中的一组统计数据：

请估计：当n很大时，摸到白球的频率将会接近 ____．（精确到0.1）