谢谢8老师上次关于我爸签证的答复！
现在我妈是美国绿卡，她在国内，请问
1: 我姐有绿卡，她帮我爸签b2 的签证成功率有多少？
-I don't know. Just try.
2: 为了保持我妈的绿卡，她一定要在美国住半年以上吗？
-Not specific. But the green card is for her to stay in US permanently, so if she travels to China too often, the CBP officer at the port of entry may give her trouble.
3: 听说过回美证，现在的规定是什么？回美证的英文翻译是什么？
-It is called reentry permit. Reentry permit can allow your mother to stay in China for > one year < two years continuously.
