What is the function of the iris in the human eye?
$(a)$ Iris restricts the light to pass the eye over to the retina
$(b)$ Iris provides protection to the eye from microorganism
$(c)$ Iris controls the size of the pupil and hence amount of light entering the eye
$(d)$ Iris allows color detection in eye

Hint - Using the idea that iris helps the pupil control the amount of light entering the eye in this problem. Iris is available in both bright and dim or low light settings. This will help to get the proper answer to this statement about the problem.

Complete step-by-step answer:

The colored part of the body is called the human body as an iris.
It helps control the amount of light coming into the eye.
The iris closes the eye when there is bright light to let in less light.
So when the light is small, the iris opens the pupil up to allow more light in.
Focuses on the retina for the light rays.

The iris muscles contract and dilate the eye's pupil to allow more or less light in.
The iris dilator muscle pulls away from the center of the iris to dilate (open) the pupil and the iris sphincter muscle pulls to constrict (close) the pupil toward the center of the iris.
Consequently, iris influences the intensity of the pupil and therefore the amount of light entering the eye.
So that's the response they need.
Hence the correct answer is choice (C).

Note – When we go into very bright light or if we attempt to look directly into the sun in the sky then our eye can not open properly because it is the iris that controls the pupil to shield the eye from the direct sun's rays. Iris color is different and is completely genetic, varying from one person to another.