原因是在中國超過半年.
-I think you may have often gone to China back and forth several times and stayed there for > 6 months recently, otherwise you would have not got the such warning just because you stayed in China for > 6 , 1 year months one time.
因為特殊原因還得回,返程票已定好來不及辦白皮書,下次回來會被沒收綠卡嗎?
-It probably you will have trouble when you return if you do not get the Return Permit, but you still can go to the immigration court to defend your GC if the CBP officer 沒收綠卡.