Which expression is equivalent to (x1/2+y1/2)(x1/2−y1/2)(x^{1/2} + y^{1/2})(x^{1/2} - y^{1/2})(x1/2+y1/2)(x1/2−y1/2)?
x−yx - yx−y
x2−y2x^2 - y^2x2−y2
x−y\sqrt{x} - \sqrt{y}x−y
x+yx + yx+y