请教各位大侠，父母持绿卡第一次回国，有几个问题:1. 有人说现在最多只能回去3个月？还是可以回去半年没有任何问题？ 2. 如果回去一年，回美国的时候只是被加注？还是根本不可以回去一年（回去超过半年,但小于一年）. 3. 如果第一回去半年，但以后某一次回去一年内回美，会有问题？
还是只是第一次回去一年内回美没问题？ 非常感谢！
-Fine, but they can not go back and forth too often, otherwise the CBP officer at the port of entry may give them trouble. The green card is for them to live in US permanently, not for use as the border-crossing card. They can not stay in China continuously for > one year unless they have reentry permit. They may apply for reentry permit which allows them to stay in China for > one year
