3. 下列哪一個等式是正確的?
(A)(a - b)2 = -(b - a)2
(B)(13 + 18)2 = 132 + 13×18 +182
(C)(a + b)2 = (a - b)2 + 4ab
(D)(s + t)(t - s) = s2 - t2.