Concept:The apparent shortening of legs is caused by refraction of light when it travels from water to air.
Explanation:Light rays from the legs move from water into air.
Water is optically denser than air.
As the rays cross the water surface, they bend away from the normal.
The brain assumes the rays travelled in straight lines.
It traces the rays backward to locate the image.
This makes the submerged part of the legs appear raised toward the surface.
As a result, the legs look shorter than their actual length.
Answer:B. Refraction.