介绍旅行计划的邮件写作 — 英语词汇题

你计划暑假和家人去昆明旅行三天。写邮件向外国朋友 Lisa 介绍旅行计划时，需要说明旅行时间。下列哪一句最适合放入邮件正文？ A. My family and I are travelling to Kunming this summer vacation. B. Kunming has a population of about six million. C. I have never heard of the city before. D. Kunming food is expensive in my opinion.