Total colorblindness is most uncommon among the people who are classified as col

    Totalcolorblindness is most uncommon among the people who are classified ascolorblind．Actually, this disability covers three different types.Some colorblind people see all colors as we usually do, except for an inabilityto see green or red．These are the people who must memorize that the top lightin a traffic signal is always the red one. Then there are others who are unableto distinguish yellow and blue. The person who is unable to see any colors atall sees the world in shades of light and dark grays. The world to him is muchlike a black and white movie.

A proper title for this passage is ________.

A．Total blindness

B．Total color- blindness

C．Distinguishing colors

D．Types of color-blindness

试题答案

答案：D