如图,四边形ABCD内接于⊙O,若∠B=130°,则∠AOC的大小是( )
A:130°
B:120°
C:110°
D:100°
Every Earth Day , We are made _____ signs to warn people to protect the nature .
将x4﹣2x2+1因式分解的最终结果是____ .