我看官方网站上是这么说的：
Have continuous residence in the United States as a green card holder for at least 5 years immediately preceding the date of filing the application 。
Be physically present in the United States for at least 30 months out of the 5 years immediately preceding the date of filing the application。
第一条说5年都要在美国，第二条又说物理上30个月以上。
我妈妈拿了绿卡，她要是每年在美国住6个月，中国住6个月。5年后能申请公民吗？
多谢！