执行下面Python代码后，输出的结果不可能是哪一项？（ ）
a = dict(zip(range(8, 0, -2), range(0, 8, 2)))
print(a)
{0: 8, 4: 4, 6: 2, 2: 6}
{8: 0, 6: 2, 4: 4, 2: 6}
{4: 4, 6: 2, 8: 0, 2: 6}
{8: 0, 2: 6, 4: 4, 6: 2}