【分析】
首先明确题目要求：给朋友Tom推荐一个适合线上旅行的城市，介绍必做活动，且至少写5句话。解题思路如下：
1. 确定推荐城市：选择有丰富文旅资源的城市，比如南京，便于展开活动介绍；
2. 开篇引入：用亲切的语气打招呼，直接点明推荐的城市；
3. 城市基础介绍：简单说明城市的地理位置、整体特色，让朋友对城市有初步印象；
4. 必做活动阐述：选取2-3个代表性的景点/活动，分别说明线上体验的亮点，丰富内容；
5. 结尾收尾：表达对朋友线上旅行的期待，让文章结构完整。
【解析】
1. 开头问候并点明推荐：用"Hi, Tom! I'd like to recommend you to have an online travel of Nanjing."开启，符合朋友间的交流语气；
2. 城市概况介绍："Nanjing is an ancient city in the east of China. It is such a beautiful and historic city!"用简单的句子介绍城市的地理位置和核心特色，同时用感叹句增强情感；
3. 必做活动详述：
介绍夫子庙："A visit to the Confucius Temple is a must if you love traditional Chinese culture."点明文化特色，适合喜欢传统文化的体验；
秦淮河游船："You can take a boat trip along the Qinhuai River and enjoy the old-time feel."描述线上体验的氛围；
中山陵景区："Zhongshan Mountain National Park is also one of the most visited tourist attractions."补充另一处代表性景点；
4. 结尾总结："I'm sure you'll love this city and even want to visit Nanjing in person someday."表达期待，让文章收尾自然，且句子数量满足题目要求。
【答案】
Hi, Tom! I'd like to recommend you to have an online travel of Nanjing. Nanjing is an
ancient city in the east of China. It is such a beautiful and historic city! A visit to the
Confucius Temple is a must if you love traditional Chinese culture. You can take a boat trip
along the Qinhuai River and enjoy the old-time feel. Zhongshan Mountain National Park is
also one of the most visited tourist attractions. I'm sure you'll love this city and even want
to visit Nanjing in person someday.
【知识点】
英语推荐类写作、城市景点描述、日常交际用语
【点评】
这篇范文语言风格亲切自然，符合朋友间的交流语境；内容充实完整，既介绍了推荐城市的基本特色，又详细列举了适合线上体验的必做活动，满足题目至少5句话的要求；句式多样，运用了感叹句、条件状语从句等，提升了文章的表达丰富度，是一篇符合要求的优秀推荐短文。
【难度系数】
0.6