Jim: Let's play volleyball, OK?
Tony: Sorry, I don't have a volleyball. But I have a basketball.
Jim: I don't want to play basketball. I only want to play volleyball.
Tony: Who has a volleyball? Do you know?
Jim: Maybe Tom has one. Let's go and ask him. （Say to Tom.）
Hi, Tom! Do you have a volleyball?
Tom: No. I don't. Does Peter have one?
Tony: Oh, yes, he does.
Tom: Hi, Peter! Do you have a volleyball?
Peter: Yes, I do. But it is at home.
Tom: Sorry to hear that!
Tony: Well, let's play basketball. OK?
Jim: OK!
Tom: Peter, please join us.
Peter: OK! Let's play!
根据对话内容，选择每个问题的正确答案。

城市聚落与乡村聚落的差异表现在(       )

某同学在“测定小灯泡的电功率”实验中，小灯泡上标有“2.5V”字样，所用电源电压保持不变，滑动变阻器上标有“20Ω 2A”字样。他正确连接电路，实验步骤正确，闭合电键后，电压表示数为2伏，电流表示数如图16(a)所示。移动滑动变阻器的滑片，当小灯正常发光时，电流表的指针偏离图(a)所示位置2小格。
①图(b)是该同学实验电路图，请你在图中补上所缺部分，并标出它的正负接线柱；闭合电键前，应将滑片P移到最____ (选填“左”或“右”)端。
②电源电压为____ 伏；当观察到____ 时，小灯正常发光；小灯的额定功率为____ 瓦。