The change in focal length of an eye lens is caused by the action of the

Options

A. pupil
B. retina
C. ciliary muscles
D. iris

Explanation

To answer the question "The change in focal length of an eye lens is caused by the action of the," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Eye Lens**: The eye lens is a flexible structure in the human eye that helps focus light onto the retina. Its ability to change shape is crucial for focusing on objects at different distances.

2. **Role of Ciliary Muscles**: The ciliary muscles are a ring of smooth muscles located around the lens. They play a significant role in adjusting the shape of the lens.

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