The Brain achieves Figure-Ground discrimination by focussing on some stimuli and suppressing others.
To me the answer to that last question is clearly "A." I always see a spiral. But I am always wrong! What we are looking at actually is "C," Concentric Circles.
If you place your finger on one circle and trace it around, you will find that you come back to the same spot each time.
Hence, physically, we can demonstrate that it is a circle. But the drive for Continuity is so great that we perceptually organize it and perceive it as a spiral.
Figure-Ground Discrimination: The transducers despite their limitations, as we discussed earlier, convert more energy from the environment than the brain can handle at any point in time.
The brain, however, engages in a separation of the input flow, whether it is visual, auditory or some other modality. Part of the input becomes the focus of attention. This is called the Figure. The rest is partially and sometimes totally suppressed from consciousness. This is the Ground or Background.