The Ponzo illusion occurs when _____.
a. a line with arrows extending away from the line appears longer than when the arrows extend inward.
b. an image that is further away appears smaller than an equal size image that appears closer.
c. lines of equal length that lie across converging lines appear to be unequal in length.
d. a circular pattern of lines and geometric shapes appears to move when gaze shifts from the center to the outside of the image.
Correct answer is option C. Explanation: The Ponzo illusion occurs when lines of equal length that lie across converging lines appear to be unequal in length.