Explanation:

- Option 4: Blue light is scattered more than red - Correct Answer

- The sky appears blue because of Rayleigh scattering. Shorter wavelengths of light (blue) are scattered more efficiently than longer wavelengths (red) when sunlight passes through the atmosphere.

- Option 1: Red light is scattered more than blue

- This is incorrect. Red light is scattered less than blue light due to its longer wavelength.

- Option 2: Ultraviolet light has been absorbed

- While the atmosphere does absorb ultraviolet light, this is not the reason for the sky's blue color.

- Option 3: Blue light has been absorbed

- This is incorrect. Blue light is scattered, not absorbed, which causes the sky to appear blue.