Judy: Lucy, who are you chatting with online?
Lucy: I'm chatting with my e-friend, Lily.
Judy: What are you talking about?
Lucy: We are talking about it.
Judy: Wow, that's cool. Where are you going?
Lucy: She likes the city of Nanjing.
Judy: I like Nanjing too. Can I join you?
Lucy: Of course! I think you two will be good friends too!
Judy: Sounds great!

【解析】：
这是一个英语对话填空题，需要根据对话的上下文来选择合适的句子完成对话。题目给出了五个选项，我们需要根据对话的内容，逐一分析每个空格应该填入哪个选项。
1. 第一个空格，Lucy正在和她的网友Lily聊天，根据选项，只有C（She is from Australia.）介绍了Lily的背景信息，适合填入此处。
2. 第二个空格，Judy问她们在聊什么，根据后文“We are talking about it.”和“Wow, that's cool. Where are you going?”可以推断，她们在讨论一个即将发生的事件。选项E（She is coming to China this summer holiday.）符合语境。
3. 第三个空格，Lucy说Lily喜欢南京，根据选项，A（She wants to travel around this city.）表达了Lily想要在这个城市旅行的愿望，与上文相符。
4. 第四个空格，Judy说她也喜欢南京，并询问能否加入Lucy和Lily的旅行。根据Lucy的回答“Of course! I think you two will be good friends too!”，可以推断Judy表达了对南京历史的兴趣，想要一起学习。选项D（I always want to learn the history of it.）符合语境。
5. 最后一个空格，Judy表示很期待和Lily见面，选项B（I can't wait to play with you.）表达了Judy的期待心情。
【答案】：
C；E；A；D；B