姐姐因在国内有事业，并且父亲年迈经常住院需要照顾，姐姐打算放弃绿卡回国。请问8老师是主动放弃绿卡好还是被动放弃好？
-Not different and the same procedure. Your sister needs to abandon her green card at any one of the US Consulates in China, and then can apply a non-immigrant visa such as B-2 visa to reenter US at the same time or later.
主动放弃是不是可以换10年签证？
另外如果放弃后，以后又想移民美国（儿子是公民)可以吗？-Yes.
谢谢！
