Do I need to bring copies of the originals submitted to the NVC?
If photocopies of original documents were not provided to the NVC with the original submission, they should be presented during the visa interview so that the original documents may be returned to you.
 
What happens to the documents submitted to the NVC?
Original documents submitted to the NVC with photocopies will be returned to the applicant(s) when the interview has been successfully completed.