module A
  def func
    p 'A'
    super
  end
end

class B
  def func
    p 'B'
    super
  end
end

class C < B
  def func
    p 'C'
    super
  end
end

B.include A

p C.ancestors # [C, B, A, Object, Kernel, BasicObject]
C.new.func # "C", "B", "A", "no superclass method `func'"