序列{20, 23, 28, 41, 61, 31, 71, 76, 15, 30}构造为完全二叉树，完全二叉树再变为最小堆后，堆所对应的的中序遍历序列可能为（）
76, 23, 41, 61, 20, 30, 31, 15, 28, 71
76, 23, 41, 20, 61, 30, 15, 31, 28, 71
76, 20, 41, 23, 30, 61, 15, 31, 28, 71
76, 23, 20, 41, 61, 15, 31, 20, 28, 71
