同学们围成一个正方形做游戏,每边站20人,四个顶点都有人,最外圈一共有( )人.
A:72
B:76
C:80
—Alice, why didn’t you come yesterday?
—I ______, but I had an unexpected visitor.
如图,△ABC与△CDE都是等边三角形,点E、F分别为AC、BC的中点.
(1)求证:四边形EFCD是菱形;
(2)如果AB=8,求D、F两点间的距离.