A:to leave
B:if that he should leave
C:if to leave
D:whether to leave
如图,在菱形ABCD中,E是AD的中点,EF⊥AC交CB的延长线于点F.(1) DE和BF相等吗?请说明理由;(2) 连接AF、BE,四边形AFBE是平行四边形吗?说明理由.