Which of the following is the best explanation of why it is difficult to discriminate the color of an object at night?

a. cones come in three types, each sensitive to different wavelengths of light.
b. the foveae are densely packed with cones.
c. at night, the amount of light entering the eye is insufficient to stimulate the cone cells but is sufficient to stimulate the rod cells.
d. as many as 100 cones may converge on one ganglion cell.

C

Explanation:

There are two types of cells in the eyes rod and cone cells. Rod cells Provide vision during the night or dim light also called of scotopic vision whereas cone cells provide vision during day time or at bright light also called photopic vision.  

Rod cells do not support the color vision that is why it is difficult to differentiate between colors.

Also, the amount of light entering the eyes is low as result cone cells are unable to stimulate.