Answer: D)The pattern of blood vessels at the back of the eye.
Explanation: The retinal scan is the techniques which is used in the bio-metric mechanism.The scanning of the retina's blood vessel pattern is capture by the scanner is the unique technique which is used for bio-metric purpose.
Blood vessel pattern is capture because it is present in unique form for every person and will help in distinguishing a person from another person while scanning.
Other options are incorrect because light reflection or reaching near retina and light pattern are not the unique way for identification while scanning a person.Thus the correct option is option(D).
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