What are “cones” in the eye and what do they do?

Cone cells, or cones, are photoreceptor cells in the retinas of vertebrate eyes (e.g. the human eye). They respond differently to light of different or color vision and function best in relatively bright light, as opposed to rod cells, which work better in dim light. Cones are mostly in the center of your retina. They help you see color and fine detail.

Explanation:

it is either c or d and i know for sure it is not a or b

c. establishing proper sleep hygiene