請問父母在國內拿到綠卡後是否必須在一定時間內來美國？
-That is not green card yet, but it is immigration visa. Your parents have to enter US before the visa expires (normally immigration visa is valid for 6 months). Your parents will get their green card status (stamp on the passpsort)immediately at the port of entry when they enter US using the immigation visa. Then, they will receive the phyical green card about one month later after their entry.
