Concept: This question tests your understanding of the anatomy and function of the human eye, specifically how it focuses light onto the retina.

Why (B) is correct: The ciliary body contains ciliary muscles that contract or relax to change the tension on the suspensory ligaments. These ligaments, in turn, pull on the lens, altering its curvature and thus its focal length. This process is called accommodation, allowing the eye to focus on objects at different distances.

Why other options are wrong:

• (A) Aqueous humour: This is a fluid that fills the space between the cornea and the lens, providing nourishment and maintaining intraocular pressure, but it does not adjust focal length.
• (C) Conjunctiva: This is a thin, transparent membrane that covers the front surface of the eye (except the cornea) and the inner surface of the eyelids, protecting the eye.
• (D) Cornea: The cornea is the transparent outer layer at the front of the eye that helps to refract (bend) light, but its curvature is fixed and it does not actively adjust the focal length.

Common Mistake: Students sometimes confuse the role of the cornea (fixed refraction) with the lens (adjustable refraction).

NEET Tip / Mnemonic: Remember that the Ciliary body Controls the Curvature of the lens for Clear vision (accommodation).

Correct Answer: (B)