class One
  attr_reader :array
  def initialize(array)
    @array = array
  end
end

class Two < One
  attr_reader :array
  def initialize
    @array = []
  end
end

array = ["D","E"]
a = One.new(array)
b = Two.new
c = Two.new

def place_string(element,location)
  if location == "b"
    take element, copy it and place it into @array in b
  elsif location == "c"
    take element, copy it and place it into @array in c
  end
end

a.place_string("D","b")

Output:
  a.array = ["D","E"]
  b.array = ["D"]