根据对话情景，在空白处填入合适的句子。

A: It's Sunday tomorrow.  1.                ?

B: Oh, I am going to watch a football match.  It's between Korea and China.

A: Wonderful! I really hope we'll win this time.  2.                ?

B: At 3 o'clock in the afternoon.  I have two tickets here.  3.                ?

A: Of course I'd love to.  But I can't.  We will have a basketball match tomorrow afternoon.

B: What a pity! 4.                ?

A: A team from No. 2 Middle School.

B: 5.                ?

A: In our school.

B: Good luck to you and your team then!

A: Thank you.  See you later.

B: See you.

自然界层次结构的主要特点？