Concept: This question tests your understanding of the structure and function of the human eye, specifically the distribution of photoreceptor cells (rods and cones) in different regions of the retina.

Why (D) is correct: The fovea (or fovea centralis) is a small, central pit in the macula lutea of the retina that is responsible for sharp, detailed central vision. It contains a high density of only cone cells, which are responsible for color vision and high visual acuity. Rods are absent in the fovea.

Why other options are wrong:

• (A) Blind spot contains only rods: The blind spot (optic disc) is the point where the optic nerve leaves the eye. It contains no photoreceptor cells (neither rods nor cones), hence it is insensitive to light.
• (B) Blind spot contains only cones: As explained above, the blind spot contains no photoreceptor cells at all.
• (C) Blind spot contains both rods and cones: This is incorrect because the blind spot lacks any photoreceptor cells.

Common Mistake: Students often confuse the fovea with the blind spot regarding the presence or absence of photoreceptors.

NEET Tip: Remember that the fovea is for 'focused' (F) and 'fine' vision, hence only cones (C) are present. The blind spot is 'blank' (B) because it has no photoreceptors.

Correct Answer: (D)