Which expression equals (x2+y2)2(x^2+y^2)^2(x2+y2)2 when simplified from (x+y)4−4xy(x+y)2+4x2y2(x+y)^4-4xy(x+y)^2+4x^2y^2(x+y)4−4xy(x+y)2+4x2y2?
(x2+y2)2(x^2+y^2)^2(x2+y2)2
(x−y)4(x-y)^4(x−y)4
(x2−y2)2(x^2-y^2)^2(x2−y2)2
(xy)2(xy)^2(xy)2