AB form and verse/refrain form are the same, aren't they?
Thank you for using the Jiskha Homework Help Forum. Since you are obviously studying music, you may appreciate the following website with a glossary of musical terminology. The AB form is at the beginning:
http://www.empire.k12.ca.us/capistrano/Mike/capmusic/glossary%20of%20musical%20terms/glossary.htm