由对话内容可知，这两个人要参加一个会议，因此没有时间去外面吃饭，所以最后决定叫外卖，由此可知他们在讨论是否要出去吃饭，故选  B 。

【听力原文】
W: Will we have time to go out for lunch?  
M: I think we should have it delivered to the office. 
W: You're right. We can't afford to be late for that conference.