Rods and cones are the photoreceptor cells of the human retina. The A  vision is the function of rods and B vision is the function of cones. The rods contain C, which is a derivative of D.

	A	B	C	D
1	Scotopic	Photopic	Visual purple	Vitamin A
2	Photopic	Scotopic	Visual purple	Vitamin A
3	Scotopic	Photopic	Visual violet	Vitamin D
4	Photopic	Scotopic	Visual violet	Vitamin D

There are two types of photoreceptor cells, namely, rods and cones. These cells contain the light-sensitive proteins called the photopigments. The daylight (photopic) vision and colour vision are functions of cones and the twilight (scotopic) vision is the function of the rods. The rods contain a purplish-red protein called the rhodopsin or visual purple, which contains a derivative of Vitamin A.