I'm afraid I can't really follow your question. You're asking weather the organic chemistry reaction is Elimination 1 or Elimination 1 cb, but I'm a little rusty on that terminology, so I don't know what E1cb is.
Also, why is this question in the High School sub-forum, when E1 is an Organic mechanism.
Also, are you asking about the organic reaction, or instead about the biochemical reaction? Because enzymes can produce reactions that can't be created in other ways. For that matter, could you be troubled to identify other reactants?
We like to help people here learn how to help themselves, that's part of the Forum Rules, link located inRed, at the top of the page. So we'd like to see some of your own work to judge how to help, for example, to answer my questions above.
And please don't offer any other info ... its very off putting to hear that all you care about is the bestest possible grade, and not about learning the underlying concepts.