At noon the sun appears white as
(a) light is least scattered
(b) all the colours of the white light are scattered away
(c) blue colour is scattered the most
(d) red colour is scattered the most
At noon the sun appears white because the light from the sun is directly overhead us. The light travels relatively shorter distance during the noon.
Scattering of light is reduced as the distance is reduced. So, the sun appears white as only a little of the blue and violet colours are scattered.
Therefore option (a) is correct