People perceive color by means of certain photopigments in the retina that are sensitive to certain wavelengths of light. People who are color blind 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 shades of red that the majority of the subjects were able to distinguish.
What this question is testing
Your task
Break the argument into its conclusion and evidence, then do exactly what the question stem asks with that structure.
Common trap
Answers that sound relevant to the topic but don't connect to the argument's actual reasoning.
Winning move
Predict what a right answer must do, then test each choice against the conclusion-evidence gap.
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