Concept:Refraction is the bending of light when it passes from one medium into another.Solution:When light from the part of the rod inside water passes into air, it changes speed and bends at the water surface.This bending of light causes the rod to appear bent or broken at the water surface.Key point: Reflection is light bouncing off a surface; dispersion is white light splitting into colours; rectilinear propagation is light travelling in straight lines (shadows).Answer:Option A (Refraction)