Answer: Hi there! My best guess for this question would be 1: All flappers prefer men who are married.
Explanation: Every other answer just doesn't feel right to me for some reason...?
With 2, the speaker never said that there were not enough single men available for flappers. In fact, they were leaving to go FOR the flappers since they were "more beautiful" than their wide-hipped and grey wives, which is why 4 makes no sense to me.
Lastly, choice 3 is just really confusing to me, so I'd rather not choose it for the sake of misinterpreting it...
Please feel free to disagree with my answer. I hope that this helps out in some way. :)