回复：十万火急:I-485能否保住学生身份

INS will process your I-140 first although you file I-140 and I-485 at the same time. If you got I-140 approved, you can adjust your status while keeping your non-immigration status. It is really rare to see I-485 rejected after I-140 approval. If your I-140 is rejected, you have no chance to go for I-485, so you are still fine with your current F-1 status. Don't worry.

The only thing is if you has no any valid non-immigration status when I-485 is rejected, you have to leav country.