WHICH TANK FILLS FIRST? ft. Simone Giertz

"But first, predictions, like _good_ little scientists."
Well, technically, I'm not a scientist, but I'll take a shot at it.  It's not going to be Tank 1, because of the outlet into Tank 2.  It's not going to be Tank 2, because of the outlet into Tank 3.  The outlet from Tank 3 into Tank 4 is stopped by gravity, so my prediction is Tank 3.