Apotential problem related to the physical installation of the iris scanner in regards to the usage of the iris pattern within a biometric system is:
a. concern that the laser beam may cause eye damage.
b. the iris pattern changes as a person grows older.
c. there is a relatively high rate of false accepts.
d. the optical unit must be positioned so that the sun does not shine into the aperture.

d)The optical unit must be positioned so that the sun does not shine into the aperture.

Explanation: Iris scanner is the capturing and scanning of the unique iris pattern that is present in small colored circle in the human eye.This techniques works through the invisible infrared light which captures the distinctive pattern.This is usually not visible from the naked eyes.

While scanning the iris through infrared light for image creation, sunlight can interrupt the aperture if it is positioned towards the direct light of sun.

Other options are incorrect because laser beam usually does not damage the eye in most cases,change in pattern in iris is rarely change over time and it has good rate of acceptance.Thus the correct option is option(d).