The correct answer is option 3: 500 nm only.

The human eye is sensitive to a specific range of electromagnetic radiation wavelengths known as the visible spectrum. The visible spectrum ranges from approximately 400 nm to 700 nm, with shorter wavelengths corresponding to colors like violet and blue, and longer wavelengths corresponding to colors like red and orange.

Option 1, which includes 200 nm and 500 nm, is incorrect. 200 nm is shorter than the visible spectrum and falls into the ultraviolet range, which is not visible to the human eye.

Option 2, which includes 500 nm and 1000 nm, is incorrect. While 500 nm is within the visible spectrum and can be perceived as a color, 1000 nm is longer than the visible spectrum and falls into the infrared range, which is also not visible to the human eye.

Option 4, which includes 200 nm and 1000 nm, is incorrect. As mentioned before, 200 nm is not within the visible spectrum and falls into the ultraviolet range, while 1000 nm is not within the visible spectrum and falls into the infrared range.

Therefore, the correct answer is option 3: 500 nm only.