In mammalian eye, the power of accommodation is controlled by changing thickness of the lens, governed by

Options

A. Cornea
B. Pupil
C. Iris
D. Ciliary body.

Answer

To solve the question about which part of the mammalian eye controls the power of accommodation by changing the thickness of the lens, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks which part of the mammalian eye is responsible for changing the thickness of the lens to control accommodation.

2. **Identify the Options**: The options given are:
- a) Cornea
- b) Pupil
- c) Iris
- d) Ciliary body

3. **Analyze Each Option**:
- **Option a: Cornea**: The cornea is the transparent front part of the eye that helps to focus light but does not change its shape to accommodate for near or far vision. Therefore, it does not control accommodation.
- **Option b: Pupil**: The pupil is the opening that allows light to enter the eye. It does not change the thickness of the lens and is not involved in accommodation.
- **Option c: Iris**: The iris surrounds the pupil and regulates the amount of light entering the eye by controlling the size of the pupil. While it plays a role in light regulation, it does not change the lens thickness.
- **Option d: Ciliary body**: The ciliary body is a part of the middle layer of the eye that contains ciliary muscles. These muscles change the shape of the lens, allowing for accommodation (focusing on near or distant objects).

4. **Conclusion**: The correct answer is **d) Ciliary body**, as it is responsible for changing the thickness of the lens to control the power of accommodation.

### Final Answer:
The power of accommodation in the mammalian eye is controlled by the **ciliary body**.