回複：最後一個問題。不盛感謝您詳盡的解釋。

我的理解對嗎？不論我是綠卡還是公民，18歲以下，孩子的綠卡如果失效，他先用B2簽證來美，我再用I485為他申請綠卡，對嗎？

-You has to file I-130 in either case. If you are green card holder to sponsor your son GC, he has to wait for the priority date to be current to file I-485 within US. But if you are US citizen, he can file I-485 any time in US. He also can apply for the immigration visa in China after the I-130 is approved.

19-21歲我要用I130為他申請，他要在中國等到I130被批，才可來美，對嗎？謝了！

-He can come to US to file I-485 if he has the valid B2 visa. He also can apply for the immigration visa in China after the I-130 is approved. Either one is OK.