The USCIS will require you show a list of documents which prove that your marriage is valid and not fraudulent.
Common Documentation
Providing all of the required documentation will make the questions easier and the process shorter.
Sample questions
If you do not bring all of the required documents to the interview, the questions will be more difficult and the USCIS officer will attempt to determine if the marriage is valid or fraudulent.
If your marriage is valid and you do not have all the requested documentation be prepared to explain why certain documetation is missing. In these situationsr hiring an immigration attorney to accompany you to the interview may be advisible.