Answer : 3. "the iris is unable to dilate the pupil immediately to be able to see things"
Explanation :

Answer: C) the iris is unable to dilate the pupil immediately to be able to see things Explanation: The size of the pupil of the automatically adjusts itself according to the intensity of light passing through it; if the intensity is more, the size is less, if less, it is more. So in our case the pupil should dilate i.e , increase in size to be able to see in the dark. This switchover takes some time. But here the entry into the dark room is immediate. So the eye has no time to adjust itself and hence is not able to see at all for a while.