Aperture of an eye can be changed by

Options

A. aqueous humor
B. vitreous humor
C. ciliary muscles
D. iris

Answer

**Step-by-Step Solution:**

1. **Understanding the Term "Aperture":**
- The aperture of the eye refers to the opening through which light enters. In the context of the human eye, this is specifically known as the pupil.

2. **Identifying the Structure Responsible for Changing Aperture:**
- The size of the pupil can change, which is controlled by a structure called the iris. The iris is a thin, circular structure surrounding the pupil.

3. **Function of the Iris:**
- The iris adjusts the diameter of the pupil. It can constrict (make smaller) or dilate (make larger) the pupil depending on the amount of light present in the environment.

4. **Purpose of Changing Pupil Size:**
- The primary function of the iris changing the size of the pupil is to regulate the amount of light that enters the eye. This helps to protect the retina from excessive light and ensures optimal vision.

5. **Conclusion:**
- Therefore, the aperture of the eye can be changed by the iris.

**Final Answer:**
The aperture of an eye can be changed by the iris.

---