Answer:
option (a)
Step-by-step explanation:
Chromatic means colour
it means it is the defect due to the colour of light.
As we know that there are seven colours of light which have different wavelength and different refractive index. As they have different refractive index, so they focus at different points on the principal axis of the lens.
As the different colours of light focus at different points so a blurred and a coloured image is seen and the defect is called chromatic aberration.