Final answer:
The black-and-white vision with greatest sensitivity under low levels of illumination is described by the 'rods' of the human eye, which detect shades of gray and function primarily under low-light conditions.
Step-by-step explanation:
The correct answer to the student's question is (D) The rods. Rods are photoreceptors located in the retina of the eye that are responsible for black-and-white vision and are most sensitive under low levels of illumination. They detect only shades of gray and are particularly effective in dim light conditions, which is why they play a vital role in night vision.
Conversely, the cones are photoreceptors that respond in intense light and are responsible for color vision. The fovea is the region of the eye with a high density of cones and is associated with acute vision, particularly in bright light conditions.
Therefore, statement (a) which suggests that rods detect color while cones detect shades of gray is false. The pupil, indicated in option (E), is not the location of rods and cones; it is the aperture through which light enters the eye, and its size is controlled by the iris according to light levels to protect the retina.