Colour blindness results from

The correct option is A Absence of cones
Colour blindness refers to an inability to distinguish between certain colors. Cones are the secondary photoreceptors and are responsible for color perception. The presence of slightly different photopigment in different cones allows them to absorb a particular wavelength more strongly than others. Brain compares the relative response of different types of cones and detects the colors. A defect in cones leads to colour blindness. Rods are the light sensitive cells that lack colour discrimination but are responsible for night vision. Eyelids serve in protection of eyeball. Retina is the innermost layers of an eyeball and contains photoreceptor rods and cones. Thus, the correct answer is option B.