The correct answer is A. Rayleigh scattering.
Rayleigh scattering is the scattering of electromagnetic radiation (of which light is a form) by particles of a much smaller wavelength. Sunlight is scattered by the tiny molecules of air in Earth’s atmosphere. Blue light is scattered more than the other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.
Mie scattering is the scattering of electromagnetic radiation (of which light is a form) by particles of a comparable wavelength. It is named after Gustav Mie, who developed a mathematical theory for this type of scattering in 1908. Mie scattering is important in many fields, including optics, meteorology, and astronomy.
Back scattering is the scattering of electromagnetic radiation (of which light is a form) in the direction opposite to the incident direction. It is caused by the interaction of the radiation with particles that are much smaller than the wavelength of the radiation. Back scattering is important in many fields, including optics, radar, and astronomy.
In conclusion, the sky appears blue due to Rayleigh scattering. This is because blue light is scattered more than the other colors because it travels as shorter, smaller waves.