分类：教育/科学-外语学习-英语考试
问题：Theyaretalkingaboutthethingsandp? 
They are talking about the things and ople_____they saw when they were in LondonA which B what C who D that
回答：D. 当定语从句的先行词既有人又有物时，关系代词必须用 that。