The answer is (c): other. This method can be seen in an mpeg video by clicking your mouse on the photograph. Well, it doesn't have time to be completed by the end of the 5 second video, but the other methods......
To see how the other methods work, here is a video inverting the bottles 180o and inverting the bottles less than 180o.
Making the water rotate like a "cyclone in a bottle" causes the water to move down faster and yet leave an air space in the center so that the pressure will equalize.
