如图所示是课本中的几个实验，按要求完成下面各题：

鸟类的形态特征与其他脊椎动物有明显的不同，最突出的特征表现在鸟类（　　）

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!

修改病句

我站在操场上，仔细地看着练习身体的同学们。