Final answer:
The correct answer to the student's question is c) Visible region; Yellow-green, as the sun's radiation peaks in the visible spectrum, with a particular emphasis on the yellow-green color due to its blackbody characteristics.
Step-by-step explanation:
The sun emits nearly 44% of its radiation in the visible region of wavelengths, with peak emission at a wavelength corresponding to the yellow-green color.
This is because, as a nearly perfect blackbody with a surface temperature of approximately 6000 K, the sun's radiation peaks in the visible part of the spectrum.
Although the Sun emits radiation across a broad range of wavelengths, which includes the infrared and ultraviolet regions, it is more intense in the red part of the spectrum than in the violet, lending the Sun its yellowish appearance. Therefore, the correct answer is c) Visible region; Yellow-green.