回复：通常485补充材料都需要补充什么材料呢? 被拒绝的可能很大吗?

Don't worry. It is not rare. At least a lot of my friends got that. And I got that.
It could be birth certificate, marriage certificate, etc. In my case, it is previous I-20 and tran.
Usually you will have 3 months to deal with that. Just give them what they asked for. My lawyer also told me that I-485 RFE is not rare and he didn't have clinet got denied after response to RFE.
Just wait for the notice. You will find it easy to deal with. Don't worry and enjoy your weekend.