【正确答案】 C

【答案解析】原文：M：Excuse me. When does flight 645 leave?W：Actually, it is delayed until 15:30.Q：What do we know about the flight?问题问的是“关于这次航班我们了解到什么”。通过对话内容可知，女士说航班推迟到15：30,故选C。