The sports meet, originally _____ this week, has to be put off because of the bad weather. [ ]

A. held

B. holding

C. having been held

D. to be held

材料一

材料二：

根据以上材料回答下列问题：

我国当前已经形成了怎样的民族关系？我国处理民族关系的基本原则是什么？