Concept:Mirages are caused by refraction of light through layers of air of different densities and refractive indices.Explanation:I. In hot weather, layers of air near the road have varying temperatures and therefore varying refractive indices. This is true.III. Light from the sky bends upward when it passes close to the hot road surface, producing the illusion of water or a reflection. This is true.II. The statement that road surfaces become invisible is an observed effect, not an explanation of the mirage.Answer:A. I and III only