A:Don’t be late next time
B:You should be blamed
C:It doesn’t matter. I’m also late
D:Never mind. Come and sit dow
如图,在正五边形ABCDE中,连接AC、AD、CE,CE交AD于点F,连接BF,已知AB=1,则DF的长是( )
河口三角洲、冲积扇均位于河流入海口,是流水堆积作用形成的.(判断对错)