____

John: Uncle Smith, this is John speaking. I'm sorry to call up so late, but may I speak to Jim?

Smith: Jim is out.____

John: OK, please. Jim and I applied to go in an adventure (冒险) tour competition on the internet a week ago. Today I was told that we were accepted.

Smith: Oh, that must be dangerous.____

John: Because we want to do sports and something exciting.

Smith: You'd better not.____

John: Uncle Smith, don't worry. We can take good care of ourselves.

Smith:____

John: Yes. We are ready for it.

Smith: Good luck.

John:____

Smith: It's OK. I'll tell him to call you back later.

John: Thank you, Uncle.

A. Are you ready for it?

B. May I take a message for you?

C. You're welcome.

D. Why do you want to do it?

E. What a great idea!

F. We will worry about you.

G. Thank you very much.

在观察玉米种子的结构时，在剖面上滴加碘液，被染成蓝色的部位是（  ）

可逆反应2NO₂2NO+O₂在恒容密闭容器中反应，可以作为达到平衡状态的标志是
①单位时间内生成n mo1 O₂的同时生成2nmol NO₂
②单位时间内生成nmol O₂的同时生成2nmolNO
③混合气体的颜色不再改变
④混合气体的密度不再改变的状态
⑤混合气体的平均相对分子质量不再改变的状态