您好。我的未婚夫正在给我申请K1签证。但是他最近发现我到美国后,如果他给我申请绿卡,他必须签署一个Affidavit.下面是他给我的内容"The Affidavit of Support is a long term commitment by all who sign it. It is legally enforceable by the U.S. government for any means-tested public benefits utilized by the sponsored foreign spouse. The obligation to support the foreign spouse ends when the foreign spouse becomes a United States citizen, has earned 40 work quarters (equivalent to approximately 10 years of working), dies, or permanently leaves the United States." 他说如果我结婚后和他离婚,10年的责任对他风险太大,他不想签这样一份东西。我想问是每一个想给他们的中国妻子办绿卡的美国人都要签这个吗?