Wow. I really hope you never get that question for real. However, one of the trick's I've learned for questions like this that delve into areas you don't want to answer or are not legally obligated to answer is to redirect it to something useful.
For example, for this question, I might turn it around by stating, "If you are asking me about my worklife balance/dedication to the job/whatever..." and continue with the new line of thought.
In this case, I might answer, "If you are asking me about how I feel about workplace relationships, I prefer not to get involved with them as I want to remain dedicated to the job at hand and avoid the complications the usually crop up in such a situation."
I see this type of question coming from two angles: 1. the recruiter is interested in you "romantically" or 2. the company wants to see how you handle absurb situations. Regardless of the angle, I think this type of question skirts a little too close to a quid pro qou type of sexual harrassment (at least in the US), and would cause me to question my desire to work for this company. There are better ways to get a date and determine how a future employee acts in an absurd situation.
So bottom line is redirect the question to something more appropriate and/or reassess whether you actually want to work for the firm in question.