綠卡丟失不去補辦，是不是意味綠卡自動放棄了？
-No. You just need to file I-90 to get the replacement ifyou are present in US now. If you are present outside US now, you need to contact the US Consulate in China to apply for a "Boarding Foil" at a U.S. Embassy or Consulate by filing Form I-131A. Then, use the boarding foil to enter US to file I-90 to get the green card replacement.
回國後多久可以辦旅遊簽證，簽成的概率有多大？
-If you get the B2 visa to enter US, you are considered abandon your green card voluntarily.
另外用綠卡回國最多可以呆多久？
-Don't stay outside US for more than 6 months.
非常感謝！
