如图所示，是由三个开关和两盏电灯组成的电路，下列说法错误的是(    )

下列几何体中主视图、左视图、俯视图都相同的是（　　）

人体的消化系统由____和____组成．

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.