Puzzle: Which Switches Which?

This is one of the puzzles i easily solved, or rather, easily answered. I was thinking twice if I should really put this one here. Actually, it's not 100% puzzle. It's a life situation brain teaser. I love puzzles like this because they are applicable in real life. Since this is a real life situation, a impossible solution is not valid and the solution should be the best and the simplest.

Rules:
Don't do foolish things that you can't do in real life. (e.g. break the wall with a rocket) You shouldn't ask somebody's help. This puzzle is only for you. And lastly, don't fool yourself with your lame solution. The solution is logical and simple. Just think!

Situation:
You are on the ground floor of a 10-storey building. In front of you is a table with 3 switches, each connected to 3 light bulbs on the 10th floor in random order. The wires, like any other household, are behind the walls. On the 10th floor, the bulbs are next to each other on the floor. Looking through the window from the outside will not give you any information about the inside. The wires were of the same color.

Question:
If the switches were labeled A-B-C and the bulbs are labeled X-Y-Z (randomly), which switch turns on which bulb?

Restriction:
You are allowed to climb up to the 10th floor only once. After that, you have to tell your answer. How would you know, which switches which?

More:
Please mail me your answers. We don't want to spoil others, right?

georel.ulangkaya@gmail.com