美国博士生拿什么签证？
C1 就是非移民签证，C1-D for study. C1 is a temporary visa and D is the status of your entry into the U.S. It's also called Cintl. The difference between these two visas are that when you enter as a CINTL， which happens at airports with international flights (not cargo)， they only have to see that there is a valid ticket in your name where it says "U.S. Bound" or similar on one leg， but not if you arrive by land from Canada/Mexico. But then once you get that Cintl visa stamped onto their I94 form， you change over to D status. So essentially this means that they needn't be sure why you came， nor do they care about how long for because after arriving at the airport you can just say you plan on applying for adjustment of status， which basically gives you an unlimited stay until USCIS decides yes or no based upon what you told them while filling out those forms. Then you must wait somewhere outside the country until either they approve or deny depending on timing， though sometimes people apply before leaving so they know well before going back to get back into the country; however this has been seen more recently to actually delay processing time， although some still prefer doing this even knowing it may cause delays. Another thing mentioned above was changing status within the USA itself – this involves filing Form I-539（and possibly other supporting docs）to adjust status， meaning go inside US borders rather than crossing at Mexico /Canada；this applies regardless of whether you entered via air or ground. If approved you will receive an EAD card confirming work authorization. However this method cannot be used unless you meet certain requirements， namely being here already on another type of nonimmigrant visa such as student，visitor etc，or married to a citizen or resident alien who filed the application for you personally.
If you come through CBP（customs）then the process works similarly but without getting an I94 form since its automatically filled out by computer. Basically all you need do now is provide enough money（about $8，000 per year）for living expenses including food，housing