建立西夏国的党项族属于哪个少数民族一支 ( )
A:匈奴族
B:回纥族
C:契丹族
D:羌族
It's generous __ ___ them to donate money to UNICEF. They think it important _____ them to help poor children go to school.
“海选”已成为我国许多农村村委会选举的重要模式。“海选”方式属于( )
在数列an中,an+1=an+2+an,a1=2,a2=5,则a6的值是 ( )