After 221g, got mail to submit original docs!!!

Hello, after 55 days of submission of documents of 221g. Now I got second mail from consulate. In this mail they ask me to submit another docs. Here I write exact line from mail.
“Further administrative processing is required on your visa application. At this time, please send your original degrees/diplomas, and project description on letterhead, and your Labor Certification Approval LCA per the instructions below.”

Now my question is " should I send my original degree certificate and marksheets?"
Should I send original LCA? If I submit original than how will I get back?
And what’s meaning of “project description on letterhead”?