不好意思，我描述的不清楚，讓您費心了。
1. "EB1a approve notice拿到後，我申請國外職位，如果國外單位提供一個offer letter" ，我這句話表達不對，我是想說我現在在中國國內，然後申請美國的職位，讓美國的研究單位提供一個offer letter, 拿到美國單位的這個offer letter後，是不是就可以直接申請移民簽證？
-Yes.
後麵就是我自己準備材料，不用美國的那個單位提供我辦理簽證的支持吧？
-You just need to write a statement addressing that you will work in your Major area as described in the I-140 in the United States, and have got the job offer from XXX University, and then provide the copy of the offer letter as part of the application materials (bring the original offer letter for the visa interview.
2.另外，移民簽證有名額或排期限製嗎？
-Yes, but if your priority date is current, that mean there is 名額 for you. 請問您Eb1a的這種也有排期嗎？
3.我看到職位申請時有一項“Will you now or in the future require sponsorship for employment visa status”，請問這個我選yes 還是No?
-Say "No" because you will be the green card holder after you use the immigrant visa to enter US. Thus, you don't need the University to sponsor your working visa.
麻煩您了，謝謝您。
