The amount of light entering the eye is controlled by the

Options

A. iris
B. cornea
C. pupil
D. crystalline lens

Answer

To solve the question "The amount of light entering the eye is controlled by the:", we need to analyze the options provided and understand the functions of different parts of the eye. Here’s a step-by-step solution:

### Step 1: Identify the parts of the eye mentioned in the options.
The options given are:
1. Iris
2. Cornea
3. Pupil
4. Crystalline Lens

### Step 2: Understand the function of each part.
- **Cornea**: This is the transparent front part of the eye that covers the iris and pupil. It helps to focus light but does not control the amount of light entering the eye.

- **Iris**: This is the colored part of the eye surrounding the pupil. The iris adjusts the size of the pupil in response to light intensity. When the light is bright, the iris constricts the pupil to reduce the amount of light entering the eye. Conversely, in low light, the iris dilates the pupil to allow more light in.

- **Pupil**: This is the opening in the center of the iris. The size of the pupil changes based on the iris's action but does not actively control light; rather, it is a result of the iris's adjustment.

- **Crystalline Lens**: This lens focuses light onto the retina but does not control the amount of light entering the eye.

### Step 3: Determine which part controls the amount of light entering the eye.
From the analysis, the **Iris** is the part that actively controls the amount of light entering the eye by adjusting the size of the pupil.

### Conclusion:
The correct answer is **Iris**.

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