Assuming that you know which switch position is on, and which off, do the following: Turn switch 1 off and switches 2 and 3 on; wait a while; then turn switch 2 off and go in. If the lightbulb is off and cold, switch 1 operated it; if it's off and hot, switch 2 did; if it's still on, switch 3 did.

David Moews ( )

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