What Happens in the Ponzo Illusion

What happens in the Ponzo illusion?

A) One bar appears to be farther away, which causes us to perceive it as larger (as compared to the other bar) .
B) One bar appears to be closer, which causes us to perceive it as larger (as compared to the other bar) .
C) Both bars appear to be at the same distance, causing them to appear to be equivalent sizes.
D) Both bars appear to be at the same distance, causing them to both appear larger than they actually are
E) Both bars appear to be at the same distance, causing them to both appear smaller than they actually are