What will happen? And why?
If you insist.It does, but what would actually happen?
But I don't see anything representing the addition of more water.What are we doing to the bottles?
If we squirt water down the yellow hose, water will come back up into bottle "a".
The blue tube connecting the air in bottle C to the air in bottle B makes it so that things will not reach the same level in bottle A. The blue tube could be 10 ft. long and the air pressure at the top of it (bottle B)would be essentially the same as the pressure at the bottom (bottle C). This makes an extension of the system. I believe the 11" length of tube d was chosen to be less than 15" so that water in bottle B would necessarily go through it and spill over from it even if the length of the blue tube was several feet long. (Another bottle could be put in the system (call it bottle D) (similar to bottle B) that the blue tube feeds into at a height several feet above this system. The water would go up an 11" tube from this bottle (because of the 15" length of tube "f") and spill right over. Clearly the water would not be at the same level as Bottle A.)This may be naive, but (assuming A is open at the top) isn't it essentially a manometer with a couple of air bubbles? So the answer is that the water level in the yellow tube must reach the same height as the water in bottle A. The details would surely depend on the initial pressure of the air in B and C.