2 is blocked at the wall of the bottle. This means that the water will never reach bottles 2, 4, and 6.
Bottle 5’s elimination: If the water flows into bottle 3, it could go in two directions from there. However, the pipe leading to bottle 5 is also blocked at the connection, so it remains empty.
Bottle 7’s trick: Many would think bottle 7 is the winner, since it is at the lowest point. But if you look at the end of the pipe above bottle 7, you can see that it is not open, so the water cannot flow into it.
The final analysis: Why is bottle 3 the runner-up?
Since water flows from bottle 1 through the open tube on the right into bottle 3 without any obstacles, and all further exits from there (towards bottles 5 and 7) are closed, the water level will rise here.
see continuation on next page
