“红军不怕远征难，万水千山只等闲。 五岭逶迤腾细浪，乌蒙磅礴走泥丸。金沙水拍云崖暖，大渡桥横铁索寒。更喜岷山千里雪，三军过后尽开颜。”

用合适的句子补全对话。

A: Hi, Wang Fei. You look very unhappy. ____?

B: I failed the math exam yesterday.

A: ____. But you don't need to worry about it all the time.

B: I really don't know how to learn math well.____?

A: Maybe you can join our math group, so that we can help each other.

B: Sounds great.____?

A: Tomorrow, if you like it. I'm sure you will be better and better. Now, don't be sad!

B: Thank you so much. ____.

A: That's great!

动物在自然界中起着非常重要的作用。利用周氏啮小峰防治美国白蛾，体现了动物具有（  ）