Question

Which phenomenon occurs when light falls on a smooth mirror? . . A). Specular reflection. B) diffusion. C) refraction . D) diffused refraction

Answer 1

Hey there!!!
your answer is going to be a, specular reflection.
hope this helps!!!

Answer 2

Reflection over a smooth surfaces such as mirrors or water leads to a type of reflection called specular reflection. Reflection over  rough surfaces such as clothing, paper etc. leads to a type of reflection called diffuse reflection.
Therefore,

Specular Reflection occurs when light falls on a smooth mirror.
So the right answer is :
A). Specular reflection.