我父母正在绿卡等候中，想要用Advance Parole Document 回国几个月。根据目前的时间，他们在中国的时候绿卡大概能下来。绿卡下来时他们不在美国会不会有什么影响？
-No as long as they have the approved AP before they leave US.
回来入境应该用AP还是绿卡？
-AP is fine. Tell the IO at the port of entry when they enter US that their I-485 is approved during their travel in China in this case. You may write a letter for them to explain it to the IO if your parents do not understand English, and then your parents just present the letter to the IO when they enter US.
