如果要你搜索与“禅让制”相关的历史资料,你可能会舍弃( )
A:尧
B:舜
C:禹
D:启
-- Do you know ______ our Chinese National Symbol of Day (国家公祭日) is?
-- Yes, it's on December 13th. It's in memory of the people_____ were killed in Nanjing Massacre.