Question

A response without a solution is tantamount to spam

Answer 1

• Switch D

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We can observe that if all four switches are used, regardless the order, it results is turning on and off of all four lights.

It means with the initial position, all lights are on, if all switches worked, the final position should be same as initial, all lights should be on.

But we see that lights 3 and 4 are off.

This is indicating that the switch D didn't work.