回複：多謝多謝！！！石油公司最可惡，綠卡的噩夢。

就是說申請perm和140期間，本人是不必在美國的，那哪個階段人必須在美國啊？

-If you file I-485, you need to come back to US. If you just apply for the immigration visa outside US e.g. in China, you do not need to come back to US until you get the immigration visa (green card).