以下程序段运行的结果是？（ ）
ls=[23,19,30,87,42,58,99,14]
ls.insert(-2,6)
[23, 19, 6, 30, 87, 42, 58, 99, 14]
[23, 19, 30, 87, 42, 58, 6, 99, 14]
[23, 19, 30, 87, 42, 58, -2, 99, 14]
[23, 19, 30, 87, 42, 58, 99, 6, 14]