What punctuation mark should be used before the choices when asking a question starting with "which"?

Question

In the following question:

Which is more expensive_ the apple or the orange?

What punctuation should I use in place of the underscore?

I have thought of a few possibilities.

Which is more expensive? The apple or the orange?

When I read it without punctuation, I kinda raise my tone in both "expensive" and "orange", so I guess I should put question marks in both places?

Which is more expensive, the apple or the orange?

The two parts belong to a single question, so there should be a single question mark at the end?

Which is more expensive - the apple or the orange?

I faintly remember that I saw something like this in books. My memory could be wrong though.

Which should be used and why?

Answer 1

Either of these is fine: Which is more expensive, the apple or the orange? Which is more expensive - the apple or the orange?

In the second version above, it should be a dash (longer) rather than a hyphen (shorter), and the point is to draw attention to this part of the sentence. See http://blog.apastyle.org/apastyle/2010/09/computer-editing-tip-em-dashes.html

However, the following format is not okay, because The apple or the orange? is a fragment: Which is more expensive? The apple or the orange?