从框里选择填入对话相应空白处的适当选项

A: Hello, this is Ann.Is that Helen ?
B: Yes, speaking.
A:Helen, The happy weekend is coming. ____ 
B: Yes, I’m not busy. I've already finished my homework.
A: ____ 
B: I’ve no idea. What about you ?
A: Let me see. Let's do something interesting and helpful. ____ 
B: Certainly. Where?
A: In the new museum.
B: Oh, I remember. I heard of it last week. ____ 
A: By bike. It's Saturday tomorrow. The traffic must be heavy, I think.
B: I agree. ____ 
A: At the gate of our school at nine in the morning.

下列各式变形正确的是（    ）

人体呼吸系统的组成按顺序应当是（   ）。