help

Hello,

Please help. I got my green card a few yeas ago. Last year, I accepted an offer from China by chance and moved back 3 months ago. I need to come to the states for a business training soon. When I go through the US immigration, what I should I say when they ask me that the purpose of my trip? Do I need to worry about losing my green card if I work in China and visit the states 2-3 times year the max? Thanks in advance.