Concept: This question tests your understanding of the different types of vision in the human eye and the photoreceptor cells responsible for them.

Why (A) is correct: Twilight vision, also known as scotopic vision, occurs in dim light conditions. It is primarily mediated by the rods, which are highly sensitive to low light intensity but do not detect color.

Why other options are wrong:

• (B) Scotopic vision is indeed twilight vision, but it is the function of rods, not cones. Cones are responsible for bright light vision and color perception.
• (C) Photopic vision is bright light vision, not twilight vision. It is the function of cones, not rods.
• (D) Photopic vision is bright light vision, and while cones are responsible for it, it is not twilight vision.

Common Mistake: Students often confuse the roles of rods and cones, especially regarding their function in different light intensities.

NEET Tip / Mnemonic: Remember "Rods for dim, Cones for color" or "Rods = Night, Cones = Day" to easily recall their primary functions.

Correct Answer: (A)