回复：Thank you all !!! & more??

I went to Canada and came back with Automatic revalidation. IO asked for my I-94 although I just gave him. He said that was not the one. It has to be the portion that says my permanent record. Otherwise he would not have allowed me in. Fortunately I kept that portion with me. He checked my expired f1's carefully, and said next time I should get my visa updated from f1 to h1 at US consulate for my safety purpose in the interior of US, whatever it means. He was polite, but made me uncomfortable doing this again.