回复:I485 RFE for F-1 Student 恳请建议
I got the same RFE. What they asked for is: tran or I-20 to prove full-time student status. I did what they asked for and was told it everything is O.K.
Just do what they ask for. I-20 or tran should be enough. Of couse you can ask your ISSS to provide a letter.
Don't worry about that. A lot of time, they just don't look at your materials carefully.