Amount of light entering the eye is controlled by:
Explanation for Correct Option:
Option C: Pupil:
Explanation for Incorrect Options:
Option A: Iris:
Light enters in the eye through iris but it does not controls its amount.
Option B: Cornea:
It focuses light ray on the retina but cannot control the amount of light entering.
Option D: Crystalline lens:
It focuses the refracted light on retina.
Hence, the correct option is option C.