It seems your wife is a US citizen to sponsor you green card. If so and she has filed I-130 already, you do not need to provide her US citizenship certificate. But if the I-130 and I-485 will be filed concurrently, she needs to provide the citizenship certificate.
x我看了皮匠老师的博客说不接受私人支票,现在还是这样吗?
-私人支票 is fine in your case.
谢谢!八老师和皮匠老师!