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   谢谢您的回答，reentry permit 会打断continuity 吗? 就是说五年重新开始计算。
--Irrelevant. If you don't have reentry permit, you will have big trouble when you reenter US if you go forth and back between US and China too often. 

但是我是打算每次不到六个月就回美国一次，这样的操作还是不行吗？因为这样可以不打断continuity？
-I think it works, but you need to have reentry permit.

谢谢