看见入籍对居留时间的规定是这样的：
Residence and Physical Presence
An applicant is eligible to file if, immediately preceding the filing of the application, he or she:
。has been lawfully admitted for permanent residence (see preceding section);
。has resided continuously as a lawful permanent resident in the U.S. for at least 5 years prior to filing with no single absence from the United States of more than one year;
。has been physically present in the United States for at least 30 months out of the previous five years (absences of more than six months but less than one year shall disrupt the applicant's continuity of residence unless the applicant can establish that he or she did not abandon his or her residence during such period)
。has resided within a state or district for at least three months
如果持绿卡已经在美住满了30个月，但未满5年。
那以后是不是只要保证每6个月入境一次，就可以在绿卡满5年以后申请公民呢？
先谢谢大家的回复。