People perceive color by means of certain photopigments in the retina that are sensitive to certain wavelengths of light. People who are colorblind are unable to distinguish between red and green, for example, due to an absence of certain photopigments. What is difficult to explain, however, is that in a study of people who easily distinguish red from green, 10 to 20 percent failed to report distinctions between many shades of red that the majority of the subjects were able to distinguish. Each of the following, if true, helps to explain the result of the study cited above EXCEPT: ['Some people are unable to distinguish red from green due to an absence in the retina of the photopigment sensitive to green.', 'Some people are uninterested in fine gradations of color and fail to notice or report differences they do not care about.', 'Some people fail to report distinctions between certain shades of red because they lack the names for those shades.', 'People with abnormally low concentrations of the photopigments for perceiving red can perceive fewer shades of red than people with normal concentrations.']