The correct answer to the question is: B) They appear to bend at the surface due to refraction.
EXPLANATION:
When light moves from optical rarer medium to optical denser medium, the light rays are bent towards the normal at the point of incidence on the refracting surface. If the order is changed, then the way will be away from the normal.
This property of light is known as refraction which is due to the fact that light has different velocities in different media.
As per the question, the object appears to be bent when it is submerged in water. Actually the object is not bent. Its the light from object which is bent at the air-water interference.
Hence, the correct answer of this question is refraction.
