回复：大侠： 请帮我看看 （好背！）

我的H1-B renewal批准， 但没有I-94。 可能是有gap between my old expiration date and resubmission date (premium processing). International office let me go back to either China or Canada to validate my new H1-B.

Q: 是否还有safety check？ 一般多长时间
-Very few cases in teh sensitive major are sujected to the background check. So, you may ignore this worry.

去加拿大还是墨西哥， 那个更好？
-Not different. choose the convenient one (travel).

应该带些什么文件？
-The H1 approval notice, the copy of the H1 petition materials(i.e. I-129 with LCA document), a employment verificattion letter from your employer (HR) and other required document based on the nonimmigration visa application form (check the US Consulate website.