OK, so this is more of a puzzle than a joke, but I figured you guys/gals would enjoy it anyway. ================================= You are standing at the bottom of a set of stairs. On the wall is a light switch with 3 switches labeled "A", "B" and "C". Each switch controls 1 light upstairs. From where you stand, you cannot see any of the lights. You are permitted to make 1 trip up the stairs. How can you determine which switch goes with which light upstairs?