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!