回复：急问b2延期，急急急，叩谢！

－－－邮寄材料里的efiling recipt是填完表格之后生成的Confirmation Receipt？还是几天之后uscis 邮寄过来的official Receipt Notice (Form I-797) ？

-It is the Efiled verification receipt (print it out) and send all the support documents with this receipt to the address indicated in the Efiled verification receipt

－－－到底是邮寄i94原件还是copy？

-Photocopy is OK.

－－－邮寄可以用usps express吗？还是普通平邮？

-If the address is mailbox, no Express Mail.