The formation of a rainbow is primarily due to the refraction, dispersion, and reflection of sunlight by water droplets in the atmosphere (Option A). When sunlight enters a raindrop, it slows down and bends due to refraction. Inside the droplet, the light is dispersed, splitting into its component colors. This dispersion occurs because different wavelengths of light refract at slightly different angles. The light then reflects off the inside surface of the droplet. As it exits, the light is refracted again, further separating the colors and creating a spectrum. The combined effect of these processes results in the circular arc of colors seen in a rainbow. The order of colors from the outer edge to the inner edge is red, orange, yellow, green, blue, indigo, and violet, with red being the outermost color due to its longer wavelength. This beautiful natural phenomenon depends on the observer’s position relative to the sun and the rain.