8老师，
这个证明信是必须提供的吗？
-Not have to if your evidences are very strong (e.g. you have a child, etc. during the marriage).
如果必须提供，是夫妻双方都要找2个证明人吗？
还是找个2个人就够了？-Yes.
证明信有格式要求吗？-No. 证明信对批准的影响大吗？-It is helpful.
我还有2个月conditional GC就要过期了，我看网上才知道I-751批准会等很久，请问等待期间绿卡过期了该如何处理？-After you file I-751 before your conditional green card expires, your conditional green card will be extended automatically for one year, and so on, until your I-751 is approved or denied.
谢谢8老师！
