What is the best expression?

Question

In case he has the at AAA Corporation, what is the most suitable expression amog the followings. I am a Japanese. Thank you.

A. He is with AAA Corporation.

B. He is for AAA Corporationthe.

C. He is from AAA Corporationthe.

Answer 1

"He is with AAA Corporation" or "He is from AAA Corporation" is also fine.  Also "He works for AAA Corporation".  

Not "He is for AAA Corporation", just doesn't make sense in this context (this is more used in the context of "His favorite baseball team is XYZ.  He is for XYZ.")

Answer 2

None of the choices you offered are good.

This is better:

He is a (job description) with AAA corporation.

頑張って！

Answer 3

He is with the AAA Corporation.