The Contrast Sensitivity Function for Chromatic Gratings Is Shifted Towards

The contrast sensitivity function for chromatic gratings is shifted towards lower spatial frequencies than that for luminance gratings, though in natural scenes the spatial content provided by colour and by luminance is the same. How did Parraga et al. reconcile this with the idea that the human visual system is matched to the properties of the world?

A) They suggested that colour is a such a late addition to vision that evolution has had no time to shape it
B) They suggested that colour is most useful when objects are large
C) They suggested that, at a viewing distance of about 40 cm, a distance at which one would pick ripe fruit, the properties of the scene and of the visual system would match
D) They suggested that colour is important in processing of coarse moving stimuli