I did the same thing. Under rewards you'll have your experience and gil and possibly a standard piece of equipment. To the right of that you'll have a list of a few more items, of which you'll need to choose one.i'm not sure i understand what you're asking me. the only selectable option was "decline" which would cancel the conversation and the quest wouldn't complete. the person would still be there with the complete quest symbol above their heads.
Took me a while to work it out as well. As GLD, it seems I can get away with selection the left most option every time.