請問一下8老師，我父母有綠卡，但目前在國內而且快1年了，還不能返回。請問有什麽辦法可以讓父母的綠卡不作廢？謝謝
-They need to return to US before their stay there reaches one year unless there is something uncontrolled to prevent their return on time such as very serious illness. Otherwise, their green card will be void.
